From an interview with Jeff Cohen, who played Chunk in The Goonies. Apparently, he regularly did the Truffle Shuffle for thousands of screaming UC Berkley fans:

After Goonies, what do you think everyone asked me to do? The Truffle Shuffle. “Hey, do the Truffle Shuffle.” “I don’t want to do the Truffle Shuffle!” Everyone just expected de facto that if I come to a party or hang out that I will lift up my shirt and shake my belly for everyone. That’s strange and I never did it. I just never, ever did it, until… I went to Berkley and I was a mic man. It’s not a cheerleader, it’s a mic man. It’s far different than a cheerleader. I had a mic, a tie, I had a hat, I didn’t lift any cheerleaders, I didn’t wear a sweater. I was a mic man and what you do is, you have a microphone and you stand in front of the student section at the football games and basketball games and you go crazy and do all these cheers for Berkley.

What would happen, it became a tradition when I was a mic man, if we were winning, like in the fourth quarter lets say, the band, this full school band, would start banging the drum and the whole band would start yelling out, “TRUFFLE SHUFFLE!” Then all the fraternity guys, who were drunk out of their minds, would yell. “TRUFFLE SHUFFLE!” Now, nothing’s quite as persuasive as ten thousand drunk fraternity dudes. If they ask you to do anything, you’re going to do it. So that was my one exception. In the fourth quarter of Berkley games, if we were winning and everyone yelled “Truffle Shuffle,” I would do the Truffle Shuffle and everyone would freak out and it was a lot of fun. But that’s it! Other than that, no Truffle Shuffle.

He also won a student government race with the slogan, “Chunk for President.”

Awesome.