This kind of thing provides you with the basic artwork and 3 panels, you choose the characters and dialogue and have at it. I chose the webcomic Red Meat because the minimalist artwork works well with this sort of thing. I know there’s others out there, so feel free to link to them.
If you want to get familiar with the strip’s oeuvre, here is the strip’s main page, and the comic creation page is here: Build your own Meat
I’ve already done three-most of the other comics here are in a foreign language and most contributors didn’t bother to stay in character, which kind of breaks the rules.