A play on the phrase tragedy of the commons. In the tragedy of the commons, each person tries to maximize their own benefit, and the end result is that everyone loses because of overutilization of limited resources. In the comedy of the commons, each person, while getting something for themselves, also (directly or indirectly) contributes back to the common good at the same time.

Someone people turn to when they're sad who makes them feel better.

slapstick, three-stooges stuff

I would assume this would be some cheap late night show like Letterman, on channel 5 possibly.

a joke that everybody copies and changes a little to seem like they made it up

because the irony of the "Tragedy of the commons" is that humans (and our mental economics) are HUGELY stupid. sobig stupid.