Earlier this week, Yahoo announced that season 6 of "Community" would get some much-needed new blood, with Paget Brewster and Keith David joining a cast that's lost Donald Glover, Chevy Chase and Yvette Nicole Brown in the last few years (not to mention prominent recurring players Jonathan Banks and John Oliver).

Now, sometimes, late-in-life TV show cast changes and/or additions can be a death knell. "The X-Files" without Mulder (and then Scully) just isn't "The X-Files," and nobody much liked either Doggett or (especially) Reyes. Ditto "The Facts of Life" trying to swap in Cloris Leachman for Charlotte Rae, or "Welcome Back Kotter" thinking they could survive without John Travolta as Barbarino.

Other times, though, a cast change can be just the shot in the arm a veteran show needs. "Law & Order" most famously made a science out of swapping actors in and out of its cast, but lots of shows have done well with either individual changes or wholesale ones. (By the time "ER" finished its run, it was on its third, and in some cases fourth, generation of characters.)

Given how well Banks fit in as Chase's replacement during "Community" season 5, and how funny both Brewster and David can be, I'm hoping they're much more Rebecca Howe than Cousin Oliver. But while we wait to see how that turns out, the HitFix TV team thought up some of our favorite late cast additions. This isn't a definitive list, but just ones that we liked, and we tried to stick with the ground rules that they be added in the fourth season or later, unless a show ran four seasons or fewer. (So Jerry Orbach wouldn't have qualified, since he joined the "L&O" cast in the third season — and also since even a fourth season addition wouldn't qualify as "late" for a show with that lifespan.)

Click through the gallery below for some of our picks, and then let me know what some of your favorite — and/or least favorite — cast changes have been.

Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "TV (The Book)" about the 100 greatest shows of all time, is available now. He can be reached at sepinwall@hitfix.com