15 Shocking Then and Now Photos of Your Favorite Sitcom Nerds

It's hard to imagine a world without classic sitcom nerds like Steve Urkel, Screech and Skippy. After all, they made us giggle the most! But now that so many years have passed since these shows ended, we're curious to see how the actors have grown up!

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Click through the gallery to see how popular sitcom nerds have changed over the years!