Big-budget Hollywood movies are typically so formulaic that you can predict every beat within the first five minutes. Which is why, in most cases, surprises are welcome. That's where the celebrity cameos come in.

From Bill Murray in Zombieland to Eminem in Funny People, celebs can make an ultimately standard flick more memorable. Here are the 25 Most Unexpected Celebrity Cameos in Movies.

RELATED: The 50 Best Celebrity Music Video Cameos, in GIFs 
RELATED: The 10 Hottest Supermodel Cameos In Movies 
RELATED: 25 Celebrities Who Look Like Iconic Cartoon Characters