I'm not sure if this would be counted as "funny" because it was one of the most frightening thing I had to experience while using UTAU, but I've been an UTAU user since December 28th of 2009. My friend donated her voice for my UTAU, and I was a complete noob back then; didn't have Japanese Locale nor the English patch so everything was in gibberish.
Well anyway, around February or March, just a few months after I created her, I made her sing Double Lariat. But my computer crashed and shut down while it was rendering. When I booted my computer and tried to get her to sing another song, it kept playing Double Lariat =A=
And it never stopped playing Double Lariat. All she would sing was Double Lariat. In any .ust.
That was horrible xD