The following is a comprehensive guide to crossover moments shared between Buffy the Vampire Slayer and its spin-off show Angel.
Buffy Season Four and Angel Season One
In the Buffy season four premiere, "The Freshman" (4.01), Buffy Summers returns back home to her mother, feeling disillusioned with her new life at college. The phone rings and Buffy answers the phone, only for the caller to hang up immediately. Buffy looks at the phone, puzzled, and walks off. Later, she goes to The Bronze, she imagines a tall, dark haired man as Angel (actually played by David Boreanaz) but is disappointed when the man gets up and it isn't him (played by another actor).
In the Angel pilot, "City of" (1.01), Angel leaves behind Sunnydale for Los Angeles. He is visited by a half-demon named Doyle who explains Angel's destiny as a future champion. While Doyle is talking, Angel has brief flashes of fighting alongside Buffy back in Sunnydale. Angel later meets Cordelia Chase at a party, a former Sunnydale resident, who is now pursuing her dream of becoming an actress in LA after her parents were made bankrupt a few months previously. Later, Angel makes a phone call to the Summers' house but hangs up immediately when Buffy's voice is heard on the other end.
In the Buffy episode "The Harsh Light of Day" (4.03), evil vampire Spike and his newly vamped girlfriend Harmony Kendall discover the Gem of Amarra in Sunnydale. The Gem of Amarra is a magic ring which makes vampires indestructible when wearing it, allowing them to go out in the sunlight without burning. Buffy manages to take the ring from Spike and subsequently asks Oz if he'll bring the ring to LA, as he has a gig scheduled there.
Oz brings the ring to Angel's headquarters in the Angel episode "In the Dark" (1.03) and is reunited with Angel and Cordelia; while meeting Doyle for the first time. However, Spike has also shown up in LA looking to get the ring back. Angel, Cordelia, Doyle and Oz later thwart Spike's plan and Angel makes the decision to destroy the ring.
Spike mimics Angel from afar
In the Angel episode, "The Bachelor Party" (1.07), Doyle sees a photograph of Buffy and admires her. Later, he receives a vision of her in trouble and warns Angel. In the Buffy episode, "Pangs" (4.08), Angel shows up secretly in Sunnydale although his presence is uncovered by Giles, Willow, Xander and Anya. Willow briefly converses with Angel about Cordelia being his secretary at Angel Investigations. When they have defeated the Chumash tribe that was attacking Buffy in Doyle's vision, Angel asks the Scooby Gang to keep his presence secret from Buffy. However, Xander later lets this detail slip while sitting down for Thanksgiving Dinner with Buffy.
In the Angel episode, "I Will Remember You" (1.08), Buffy is reunited with Angel and Cordelia and introduced to Doyle when she shows up at Angel Investigations offices. She expresses her anger at Angel not informing her of his presence in Sunnydale but later helps him fight a Mohra demon.
In the Angel episode, "Parting Gifts" (1.10), Angel and Cordelia are reunited with Wesley Wyndam-Price. The two has previously known Wesley as a replacement Watcher for Giles in Sunnydale, who was incompetent in his training of Slayers Buffy and Faith Lehane. Despite still showing some of this incompetence, Wesley joined Angel Investigations.
In the Buffy episodes, "This Year's Girl" (4.15) and "Who Are You?" (4.16), rogue Slayer Faith Lehane wakes from her seven month coma to cause havoc in Sunnydale, deliberately swapping bodies with Buffy in the process. When Buffy gets her body back, Faith runs off and is seen leaving on a train from Sunnydale.
In the Angel episode, "Five by Five" (1.18), Faith shows up in LA and is hired by Lindsey McDonald, Lilah Morgan and Lee Mercer of Wolfram & Hart to assassinate Angel. Faith tortures Wesley but later breaks down in Angel's arms, feeling remorseful for all the harm and murder she's caused. This continues into the next episode "Sanctuary" (1.19), where Faith searches for redemption. She is interrupted by an angry Buffy who shows up at Angel's home, following Angel's offscreen phonecall to Giles about Faith being in LA. Buffy attacks Angel for trying to help Faith and he bites back at her, telling her to keep out of his life.
A jealous Riley feels threatened by Angel
In the Buffy episode, "The Yoko Factor" (4.20), Angel returns to Sunnydale to apologize to Buffy about his anger at her regarding the Faith situation. He also meets Buffy's new boyfriend, Riley Finn. The two express a mutual jealously of each other.
In the Angel episode, "Blind Date" (1.21), Cordelia can be seen conversing over the phone with Willow over decrypting computer files. Cordelia is trying to break into Wolfram & Hart's files while Willow is trying to break into The Initiative's files to stop Adam in the Buffy episode "Primeval" (4.21). However, Willow's side of the phonecall is not shown on either show.
In the Angel episode, "To Shanshu in L.A." (1.22), Angel's sire and former lover Darla is resurrected from the dead by Wolfram & Hart, having originally been killed in the Buffy episode "Angel" (1.07). Darla was previously seen in flashbacks for the Buffy episode "Becoming, Part One" (2.21) and Angel episodes "The Prodigal" (1.15) and "Five by Five" (1.18) before this, however.
Buffy Season Five and Angel Season Two
In the Angel season two premiere, "Judgement" (2.01), Angel goes to visit Faith in prison after handing herself following the events in Sunnydale and LA months previously, post-coma.
Darla, Angel, Drusilla and Spike cause havoc in China
In the Buffy episode, "Fool for Love" (5.07), Spike recounts his past to Buffy when she becomes interested in knowing how he killed two Slayers before him. Meanwhile, over on the Angel episode "Darla" (2.07), Angel remembers some past events about his time with Darla; some of which overlap with Spike's story. In both episodes; Darla, Angel, Drusilla and Spike make flashback appearances. The Master, who acted as a villain in Buffy's first year at Sunnydale High, and killed by her in the Buffy episode "Prophecy Girl" (1.12) also makes an appearance in the flashback scenes of "Darla".
In the Angel episode, "The Trial" (2.09), Drusilla makes her first present tense appearance on Angel, employed by Wolfram & Hart to resire Darla. Drusilla continued to make appearances in "Reunion" (2.10) and "Redefinition" (2.11) before returning to Sunnydale in the Buffy episode "Crush" (5.14) where she asks Spike to come join her in LA with Darla. When Spike declines, announcing his love for Buffy, Drusilla runs off and she is not seen in any present tense scenes in either show; although the First Evil would take her form and she would also appear in flashbacks for both shows. Harmony is also disgusted to hear that Spike is in love with Buffy and also runs off (making her final appearance on Buffy the Vampire Slayer). She later appears in LA to visit old pal Cordelia in the Angel episode "Disharmony" (2.17). Cordelia is unaware that Harmony has since been made a vampire and mistakes her for a lesbian instead. Cordelia makes a phonecall to Willow the next day and asks why she didn't inform her about this. Willow can be seen on the other end of the phone, brushing her teeth in her UC Sunnydale dorm room with a shocked expression on her face and warns Cordelia about Harmony's newfound vampirism. Cordelia laughs and makes a mild slur about thinking Harmony's a lesbian, only to be informed by Willow herself that she is now a lesbian. Willow then makes a phonecall to the Hyperion Hotel about Harmony's vampirism but her side of the call is not shown onscreen.
In the Buffy episode, "Forever" (5.17), Angel meets with Buffy at the graveyard to provide comfort following her mother's funeral. He provides comfort and the two share a kiss.
A distraught Willow gives Angel some bad news
In the Angel season two finale, "There's No Place Like Plrtz Glrb" (2.22), a happy Angel, Cordelia, Wesley, Gunn, Fred and Lorne have returned from Pylea, back home to the Hyperion Hotel. Their happiness is crushed, however, when a silent grief stricken Willow is seen in the hotel lobby, about to inform them of Buffy's death.
Buffy Season Six and Angel Season Three
For its sixth season, Buffy moved to network UPN while Angel remained on the WB. The shows aired on different nights and different channels and because of network rivalries, direct crossovers between the shows were banned. However, references between the two shows are still made.
The season three premiere of Angel, "Heartthrob" (3.01), sees Angel spend the Summer between the second and third season at a retreat, grieving Buffy's death. At the end of the episode, Angel and Cordelia discuss Buffy's death some more with both agreeing that they miss her but that she would have wanted Angel to move on and not brood over her.
In the Angel episode, "Carpe Noctem" (3.04), Angel is sitting in the garden of the Hyperion Hotel with Fred when Cordelia runs out telling Angel that Willow called and that Buffy has been resurrected from the dead. In the Buffy episode, "Flooded" (6.04), Buffy takes a phonecall offscreen. When she returns, she announces that Angel has called and wants to meet her between Sunnydale and LA. She takes off to meet him at the end of the episode.
We are never shown the conversation between the two but it's implied that it didn't go well with Angel returning from their meeting in the Angel episode "Fredless" (3.05), grumpy and looking for comfort food in ice-cream. In the Buffy episode "Life Serial" (6.05), a downcast Buffy returns from the meeting with her own comfort food in fried chicken.
Buffy Season Seven and Angel Season Four
In the Angel episode, "Salvage" (4.13), Faith is in prison when she is attacked by a fellow inmate, holding a knife the same make as what the Bringers were using in Sunnydale to get rid of Buffy and the Potential Slayers. This is the first and only time the First Evil is present on Angel but there is some ambiguity with visions of the deceased Lilah and Darla appearing before Wesley and Connor respectively; although this may be a catalyst of Wesley's gradually unstable mind and Darla claims she was sent by the Powers That Be . Faith is then encouraged by Wesley to break out of prison and help fight Angelus and the Beast . Faith agrees and returns to the hotel with him, appearing in the episodes "Release" (4.14) and "Orpheus" (4.15). Angelus, later hearing about a Slayer being present in LA, calls the Summers' house to see if Buffy's there, Dawn answers the phone although Dawn's side of the call is not shown on either show. This is the only time Angel is ever seen contacting Dawn, she didn't exist until the fifth season of Buffy but everyone who met anyone from the Summers family had their memories modified to include Dawn.
In the Buffy episode, "Lies My Parents Told Me" (7.17), the phone rings and Andrew answers it. He informs Willow that a "feminine sounding" Fred wants to speak to her. Willow then goes down to the basement and tells Willow that she needs to leave but will inform Buffy about everything when she gets back. In the Angel episode, "Orpheus" (4.15), Willow meets with Angel Investigations, announcing that Fred called her to help restore Angel's soul, she having done it five years previously in "Becoming, Part Two". She is seen to have a friendly relationship with Fred, Gunn and Wesley and is also unsurprised by Angel's teenage son Connor who shows a distrustful attitude towards her and her magic. Willow is also reunited with old school friend Cordelia (although Cordelia is now possessed by the evil higher power Jasmine) and successfully restores Angel's soul. Willow then takes Faith back to Sunnydale in order to fight The First.
In the Buffy episode, "Dirty Girls" (7.18) Willow and Faith return from LA and Faith remains with the show until the series finale, "Chosen" (7.22).
In the Angel season four finale, "Home" (4.22), Angel acquires an amulet from the ghost of Lilah Morgan so that The First Evil's apocalypse doesn't clash with Wolfram & Hart's. Angel appears in Buffy's final two episodes "End of Days" (7.21) and "Chosen" (7.22), giving Buffy the amulet and claiming his love for her. Buffy gives Spike the amulet and he is killed while wearing it.
Angel Season Five
In Angel's fifth and final season, Buffy was no longer on the air. However, there are some brief crossovers. Spike is resurrected from his death because he was wearing the amulet, although he is in incorporeal form. Spike becomes a main character for the remainder of the season, helping the Angel Investigations team. His ex-girlfriend Harmony Kendall is also made secretary for Wolfram & Hart and also becomes a main character. Both characters appear in the season premiere "Conviction" (5.01). The events of Buffy's "Chosen" are also recounted in this episode.
In the episode "Soul Purpose" (5.10), Angel dreams of Spike and Buffy having sex although Buffy's face is not seen and her dialog is taken directly from the Buffy episode "The Prom" (3.20).
In the episode, "Damage" (5.11), Angel's team deal with the Slayer Dana. Prior to the events of this season, there were only two Slayers - Buffy and Faith - but Willow cast a spell in "Chosen" to activate all Potential Slayers into real Slayers. Wesley is informed by Giles offscreen that their best man will be sent to help them and turns out to be Andrew. Andrew explains to Wesley that himself and other Sunnydale alum have formed their own organisation, following the destruction of the Watcher's Council, to train all the World's Slayers. Andrew tells Spike about what the others are doing - Xander's in Africa, Willow and Kennedy are in Brazil, Buffy and Dawn are in Rome, and everyone else is in England. Andrew later tells Angel that none of the Scooby Gang trust Angel now that he runs Wolfram & Hart.
In the episode, "The Girl in Question" (5.20), Angel and Spike visit Buffy's apartment in Rome only to find Andrew there. He tells them that he now lives with Buffy and Dawn and that Buffy is out partying in a club. When Angel and Spike arrive at the club and are disheartened to see Buffy dancing from afar withThe Immortal. The Immortal had previously slept with Darla and Drusilla.