"I heard Daft Punk is going to be playing at the trash fence." - said nobody funny.
It's the equivalent of "why did the chicken cross the road?" A joke whose humor value is impossible to calculate because you've heard it a thousand times, which is exactly 999 too many.
It's not a secret where it started, but I found out for myself this year by accident, and it was hilarious. I was at Camp Neu Verboten, hanging out with the camp leader Omar, waiting to DJ a set for them, and we were chatting. Somehow the Daft Punk joke comes up and as it turns out, it started in this camp.
Camp Neu Verboten (formerly just Verboten) does a series of one-hour sets of everything from Kraftwerk to the Eagles to Depeche Mode to, of course, Daft Punk. They've been doing that since the early 2000s.
In 2009, the guide showed them as having a Daft Punk-Kraftwerk night on Thursday, as they had the previous year, in their approximately 750 square foot tent. All that day, people were stopping by camp to confirm that Daft Punk would be there that night. By evening, there were hundreds of people outside (Esplanade @ 4:30) waiting to see DP, and the camp members were trying to let people know that no, Daft Punk was not playing their little space - only DP music.
Around 10:30 the crowd rushed the tent and tried to pack itself in, though obviously that many people aren't fitting into their tent. They played about 30 mins of Daft Punk before a Ranger came in and told them they had to disperse the crowd as it was completely blocking the 4:30 intersection. Shouting at the crowd, including with bullhorns, didn't convince them to leave, however. They weren't going to miss the chance to see DP!
Finally, Omar had to resort to sonic warfare, playing Que Sera Sera (Doris Day), then Yummy Yummy (Ohio Express), and eventually an apparently rousing march version of "Jesus Loves the Little Children" before just shutting down completely for the night.
The best part of hearing this story from him was that we were sitting on a couch in front of their camp, while I was just finishing chuckling over it, two girls pulled up on bikes and inquired, "Is this where LCD Soundsystem is playing tomorrow night?"
You can read Omar's first-hand account of it on the eplaya forums, from back in 2009.