Boreanaz left the show after its third season to headline his own spinoff, but came back for the last episode of BtVS to say farewell to the show that launched his own. Angel came into town to help his soulmate Buffy in her battle with The First Evil, and in the process ended up discussing the state of their relationship (including expressing disbelief about her current love interest Spike). Buffy compared herself to cookie dough as a way of explaining she wasn’t ready commit to anyone, even him. This was the last time the two shared the screen together — Sarah Michelle Gellar was supposed to guest star on Angel’s penultimate episode, and Boreanaz was publicly miffed when she did not.
5. Eriq La Salle, Sherry Stringfield, Laura Innes, Alex Kingston, and Hallee Hirsh on E.R.
It’s hard to imagine a show that had more cast changes than this long-running medical drama. So perhaps George Clooney decided to bid farewell to the show that launched him into superstardom three episodes before the series finale, so as not to steal the limelight from other actors who returned to pay their respects. The actual swan song featured former County General doctors Benton, Weaver and Lewis returning to celebrate a medical clinic opened by Dr. Carter (Noah Wyle, the cast member who had the longest run on the show). Dr. Corday also came by with the late Dr. Greene’s daughter Rachel for her medical school interview. The series came full circle when Carter taught Rachel how to put in an I.V, just as Benton had done for Carter in the pilot. Interestingly, because E.R. was on the air for so long and had such a revolving door of actors, the returning characters were barely integrated with the regulars, since the newer staff had no idea who they were, and so had no history with them.
6. Jane Lynch on Party Down
The creators or the Starz comedy wrote the last episode of the second season so that it could be aired as the series finale (which it was, alas). So it was fitting that the Party Down crew’s last event would be to cater the wedding of their former co-worker, the lovably daffy Constance Carmell, played by Lynch. She left the show in the middle of the first season, and despite her new A-list status, returned to the struggling show as a guest star the following season. Besides providing bittersweet closure to the misfit caterers, the episode gave a beloved returning character the rare chance to evaluate her replacement — Megan Mullally’s silly stage mother Lydia — and like the audience, find her not quite up to snuff.
7. Jason Priestley, Tiffani Thiessen, and Gabrielle Carteris on Beverly Hills, 90210
In the final episode of the series, perennially on-again, off-again couple David and Donna got married, an occasion that brought back former Beverly Hills residents, Valerie and Andrea, and inexplicably, West Beverly High principal Mrs. Teasdale. It was understandable for Brenda not to show up, since Shannen Doherty was persona non grata on the set. Much more surprising is that her twin brother Brandon was also a no-show. Instead, he sent in videotaped messages that were shown at the couple’s bachelor and bachelorette parties. Why Jason Priestley felt it was important to appear in the last episode, but could not actually interact with his former castmates is unclear. C’mon Brandon! Not cool.
8. Amanda Seyfried and Aaron Paul on Big Love
The easiest way to have a character leave a show, but leave the door open for a return, is to have him or her get married and move away. Such was the case for Sarah, the oldest daughter of the polygamist Hendricksons clan. Her portrayer left the series as her movie career heated up, while her TV husband moved onto an even more critically acclaimed show, Breaking Bad. The two were back for the final scene of the finale, picking up eleven months after Bill’s death. Scott and Sarah returned for their baby’s christening, and Sarah and Barb shared a moment reflecting on how Bill was responsible for their unusual yet loving family unit. This moment, while moving, was jarring when thinking about how these two were the most vocal in their discontent with Bill. As for Sarah’s sister Teenie, she merited a jokey shoutout in which we learned that she’s been in the bathroom since season 4.
9. Rob Lowe on The West Wing
Like most shows with sprawling casts, there were a lot of comings and goings during the political drama’s seven-year run. But the exit of Sam Seaborn, President Bartlett’s Communications Director, had the most impact. Although his character was a fan favorite, Lowe originally signed on to the show as the lead, and was unhappy that the show evolved into an ensemble series. He departed not long after show creator Aaron Sorkin did, but both returned for the finale: Sorkin, known for his witty, rapid-fire scripts, makes a wordless cameo during the new president’s inauguration, while Seaborn comes back to work in the White House, this time as Deputy Chief of Staff.
10. David Duchovny on The X-Files
Some characters are so fully woven into their series, it is unimaginable to think of a show without them. Think Cheers without Sam Malone, Friday Night Lights without Coach Taylor, The X-Files without Fox Mulder. Yet the latter iconic character did leave at the end of season 7, woefully replaced by a pair of FBI agents who who did not have an ounce of Mulder’s charisma or his pathological interest with the mysteries at hand. While Duchovny made occasional appearances in the last two seasons of the show, he was the main focus of the series finale. Mulder and Scully become fugitives after he escapes a military tribunal that sentenced him to death. The show ends with Mulder and Scully lying together in a motel room, ruminating on Mulder’s motto, “I want to believe.” The phrase could have applied to shippers, who spent the series hoping the agents end up together. Although the finale ended on an ambiguous note in regards to the fate of the world, the status of Mulder and Scully’s relationship was much more conclusive.