Years ago, I had this running gag with a girlfriend that I was the host of a talk show. It came from the set up of this room at the Smithsonian that we used to hangout in, so that we were sitting side by side in chairs. Anyway, the format allowed me to ask a lot of jokey, probing questions and I’d make asides to the ‘audience.’ Typing it, it sounds creepy, but we used to really have fun sitting in the free musuem goofing around (I was in my 20s and broke, it was great and free date)
I’ve done a mock “DVD/Blu-Ray Director’s Commentary” at a party with my friends before, which was a lot of fun.
For example, we’d be sitting around the table and one of my friends would pour themselves a glass of whiskey on the rocks and start drinking it, and I’d say something like “Now believe it or not, it took six takes to get this shot right. The thing is, that whiskey colour doesn’t actually translate well onto camera in ambient party light, so we had to blend it with a mixture of cat urine and used teabag strainings to get the right effect…”
Of course, my friend is sitting there with a mouth full of whiskey going “Wait, what?” and everyone else is cracking up. It’s hard to convey the full effect in a text-based medium, though.
Thanks for the answers everyone, I love the similar examples in this thread. 
In some ways, those random flash mob dance performances are kind of like breaking the fourth wall…
People who talk to God aloud outside of churches are usually considered…weird.
Dr. Peter Venkman: And then she threw me out of her life. She thought I was a creep, she thought I was a geek, and she probably wasn’t the first.
Dana Barrett: You are so odd.
I think foisting an amateur dance performance on the general public could be seen as erecting a 4th wall if anything. If I was to punch one of the mob, that might be breaking the wall.