The Twitch streamer CodeMiko almost always has a donation goal to make her avatar fart. I've never caught one live, but she streams pretty often and is popular, so there's no way it doesn't happen pretty often. Here are some examples:
https://www.youtube.com/watch?v=QMGLJrOq1Cc
https://www.youtube.com/watch?v=lp3UlGDcWy4
She also farts on stream for real, but always mutes it.
