WATCH: Did X-Men: The Animated Series give birth to the MCU?

During the late '70s and throughout the '80s, the X-Men became one of Marvel's most popular comics. But it wasn't until 1992 that the characters truly became pop culture icons in X-Men: The Animated Series. Fox didn't initially realize it had a hit on its hands, but X-Men quickly won over legions of fans while paving the way for the X-Men live-action movie in 2000.

The first X-Men film is credited with starting the modern era of superhero movies, which hasn't slowed down yet. But it was the cartoon that gave fans the shared universe of the comics. X-Men and Spider-Man: The Animated Series took place in the same world. But the thing that really made X-Men special is the way it threw in additional characters for seemingly minor appearances. Doctor Strange, Thor, Ghost Rider, Deadpool, and more showed up for brief moments, but those moments established a universe that was much larger than just the mutant heroes and villains. It was essentially an animated MCU.

One of the key reasons for X-Men's abundance of guest stars was writer and producer Larry Houston. He was a part of the creative team that refused to let X-Men get dumbed down with talking cars and silly animals. More importantly, Houston understood the mythology of the comics more than anyone else on the show and put that knowledge to good use. And as explained in our video, Houston came up with a way to get around Marvel's character restrictions.

For more info about X-Men: The Animated Series, check out the full video!