Not quite a "GO BILLS!" moment, but it was something I'll never forget.
Back in the mid-to-late 90's I was at Disneyland. One night in Toon Town the characters were having fun with what was left of the crowd.
Dale, of Chip 'N Dale, took my Starter Bills jacket that I had draped over my chair and put it on. I'll never know how it fit him, but it did.