The Batman Villain Everyone Forgot The Big Bang Theory's Johnny Galecki Played

As Leonard Hofstadter in "The Big Bang Theory," Johnny Galecki wants to talk nerdy to you. All geeky topics are welcome and tabled for discussion, as Leonard and the gang debate everything — including superheroes from both Marvel and DC. Yet, this isn't Galecki's only rodeo with comic book-related matters, as he once played the Batman villain Knux in the "Batman Beyond" animated series.

Set in the future, "Batman Beyond" sees Kevin Conroy's Bruce Wayne officially hang up his cape and cowl, as Terry McGinnis (Will Friedle) becomes the Batman of the Future and protector of Neo-Gotham. Bruce is still around, but he takes up more of an Alfred Pennyworth role, being Terry's eyes and ears from the comfort and safety of the Batcave. Several villains from Bruce's past feature, but since the bulk of them are retired or on arthritis medicine by this point, the series introduces new rogues for Terry to slug. As a matter of fact, a good chunk of the best "Batman Beyond" villains are fresh additions to the lore.

In the Season 2 episode "April Moon," Galecki voices Knux, a cybernetic-enhanced villain with hammer-like fists and key member of Bullwhip's April Moon Gang. The gang's story is that they threatened Dr. Peter Corso into giving them upgrades that would aid them in their life of crime. The goons, including Knux, give Terry a hard time, but a fail-safe word ends up being their undoing, resulting in their enhancements self-destructing. It's further proof that crime doesn't pay, even in Neo-Gotham.

While Johnny Galecki's appearance as Knux in "Batman Beyond" was a one-and-done deal, he had another chance to go toe-to-toe with a popular Batman actor as Leonard in "The Big Bang Theory." In the Season 9 episode "The Celebration Experimentation," which also happens to be the show's 200th episode, the late Adam West cameoed as himself in a story in which he attends Sheldon Cooper's (Jim Parsons) Batman-themed birthday party.

A memorable car scene sees Leonard and West argue about who is the best Batman actor. Leonard can't believe that West says Michael Keaton is a better Dark Knight than Christian Bale, as West quips back, "Even my poodles know that Bale is overrated." West argues that due to his Batman having a sense of humor, he thinks that his version of the character should be at the top of the list followed by Keaton, Val Kilmer, Lego Batman, Bale, and finally "that pretty boy" George Clooney.

For Galecki, he cherished the opportunity to share the screen with West. "He's a hero of mine," Galecki told Variety in 2016. "I was such a huge fan of that show growing up." But how did Adam West really feel about his guest role on "The Big Bang Theory"? He enjoyed himself, and why wouldn't he? He was, and always will be, Batman. KA-POW!