Gaga's ice bucket challenge tops them all

Gaga, Oprah, Ronaldo, Steven Spielberg and Charlie Sheen are the latest big name celebs to take on the challenge.

You may recall we told you all about the ALS Ice Bucket Challenge last week, but if you were out sick that day, here's a handy recap:

The idea is to grab a bucket of ice water and throw it over yourself, then nominate three other people to do the same thing, with the video posted to YouTube, Facebook or Instagram. Anyone who is challenged must do the same thing within 24 hours or donate $100 to the ALS Association (most people do both).