While it looks glamorous from the outside, the world of TV is relatively small, and the actors who work in it often find themselves on the same sets more than once.
TV has produced stories that are near and dear to the hearts of millions Americans. Once in a while, producers get the chance to reunite the figures in those stories again later on down the line. For fans, the perceived or imagined real-life relationships between actors is a precious thing, and seeing them come back together can bring a smile to their face all on its own.
While fans sometimes wish that shows would just go on forever, or reboot immediately, it's rarely that simple. TV shows are a huge gamble for the companies that make them, and they are viewed as having a distinct expiration date. However, bringing one actor's former co-star onto their new show has a built-in kind of marketability. It's easy to imagine that the fans of a defunct show will tune in to a new one just for the promise of seeing their favorite actors on screen together again, even if they're playing different characters.
Of course, there are horror stories in Hollywood as well. Some actors may have worked together for a decade or more without becoming friends, and seeing them back together is just plain awkward. Others, still, may flat out refuse to work together. Even in these instances, fan outcry can be consistent, and what the networks and studios see as a chance at profit will often come to pass anyway.
Here's a look at some of the best actor reunions on TV.
'Friends' on 'Cougar Town'
Few TV programs have matched the massive success of Friends. Courtney Cox's new show, Cougar Town, has tried -- bringing in her former co-stars Jennifer Aniston, Lisa Kudrow and Matthew Perry for guest appearances all on separate occasions.
Mindy Kaling and B.J. Novak on 'The Mindy Project'
Mindy Kaling and B.J. Novak had some of the most singular moments on The Office as the incompatible couple Kelly and Ryan. Years later, they showed at least a little more chemistry when Novak played one of Kaling's boyfriends on The Mindy Project.
Alyson Hannigan and Seth Green on 'How I Met Your Mother'
In the 1990s, Alyson Hannigan and Seth Green appeared together in Buffy the Vampire Slayer. A decade and a half later, they were on screen together again under very different circumstances. Green made a guest appearance in one episode of How I Met Your Mother as a creepy college friend of Marshall and Lily Erikson.
Drake Bell and Josh Peck on 'Grandfathered'
Drake Bell and Josh Peck made their names together on Nickelodeon, first on the Amanda Show and then on Drake & Josh. They had a rocky friendship in the years that followed, though they showed their fans that all was well when Bell showed up on Grandfathered in 2016.
The 'Seinfeld' Cast on 'Curb Your Enthusiasm'
Seinfeld producer Larry David brought Jerry Seinfeld, Julia Louis-Dreyfus, Michael Lewis and Jason Alexander all back together again on his HBO series Curb Your Enthusiasm.
The 'Glee' Cast on 'The Flash' and 'Supergirl'
Last year, Darren Criss reunited with his Glee co-stars Grant Gustin and Melissa Benoist on their respective superhero shows -- The Flash and Supergirl.
Jon Hamm and January Jones on 'Last Man on Earth'
AMC's hit series Mad Men wasn't always kind to its female characters, but January Jones got her onscreen revenge on Jon Hamm when he appeared briefly on Last Man on Earth, before she promptly shot him.
Allison Janney and Bradley Whitford on 'Mom'
Allison Janney and Bradley Whitford faced trial by fire together as fast talking White House aides on The West Wing. They got to do some more leisurely scenes together last year when Whitford appeared on CBS's comedy Mom.
Kaley Cuoco and Katey Sagal on 'The Big Bang Theory'1comments
Katey Sagal played Kaley Cuoco's mother on the short-lived comedy 8 Simple Rules in the early 2000s. The two got to reunite under similar circumstances on The Big Bang Theory, where Sagal played Cuoco's mother during her wedding to Leonard.