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Mary-Kate and Ashley Olsen

Observant fans could tell whether it was Mary-Kate or Ashley appearing in any given scene. Although they are very similar looking, they are not actually identical. The fraternal twins have a few differences. Mary-Kate is left-handed and Ashley is a righty. Plus, Ashley has a freckle above her lip.

'Full House' 25 Years Later: What You Never Knew About the Iconic Show

On September 22, "Full House" celebrates its 25th anniversary. Here are 20 fun facts that you probably never knew about this squeaky clean, well-loved family sitcom.