Today is Ellington Ratliff's 23rd birthday! While you probably know the musican mostly from R5, he actually used to act — and even appears in the pilot episode of Victorious back in 2010. Spoiler: he looks so different.

Obviously, we're huge fans of the Nickelodeon show, but even if you think you know everything about it, you may have missed some of these guest appearances.

Click through the gallery to see celebrities you didn't know were on the show. Let us know which cameo shocked you the most in the comments!