TV often uses flashbacks to provide new insight into the characters we know and love.
Some shows use them all the time, but in this slideshow we're looking at the shows where they were more of a special occurrence.
In many of these we were treated to costumes and hairstyles on the current actors to make them look younger, but in some cases casting younger actors was necessary to pull it off.
Which flashbacks are the most memorable to you?
1. The Big Bang Theory
Thanks to flashbacks, we got to see how Leonard and Sheldon came to be roommates, and more importantly, how the elevator was broken! Leonard's story helped clear up why anyone would put up with Sheldon for so long. though why Leonard didn't run for the hills during Sheldon's interview we still don't understand.
2. Grey's Anatomy
"The Time Warp" episode of Grey's gave us a chance to see a meek Bailey before she became "the Nazi," Ellis and Richard's illicit affair, and Callie as a resident. We also learned that Callie and Alex even hooked up once!
3. Buffy the Vampire Slayer
Buffy did the flashback thing a few times, but arguably the most memorable was Spike's story in "Fool for Love." A nearly fatal mistake prompted Buffy to ask Spike about the two slayers he killed, but we received much more than that. We watched the vampire's transformation from nerdy human to the ruthless killer he became.
4. Friends
Every time Friends did a flashback it was memorable. From the prom video where we learned Ross and Rachel were each other's lobsters to literally any instance of "fat Monica." Throw in Rachel's pre-surgery nose, Ross's mustache, and Chandler's "Flock of Seagulls" haircut and you've got the makings of a memorable episode.
5. The Simpsons
Sure it's animated, but that doesn't take away the enjoyment of getting to see what Homer looked like before he was fat and bald. "The Way We Was" told the story of how one of our favorite TV couples first got together. Marge may have made the wrong choice for her prom date, but she picked the right guy to marry!
6. Criminal Minds
For years fans wondered if orginal BAU member Jason Gideon would ever reappear. While the actor had no intentions of returning, the character finally did via flashbacks in which he was played by Ben Savage. Fans learned how he and Rossi started the unit as they investigated their old friend's tragic murder.