Ideas for what to build at the meetup. Grab one as-is, mash two together, or use it as a starting point.
One person sets it up, everyone else joins in. Each one starts with something small to answer, and the replies are the post.
Post a weird picture. Everyone names it as if it were an album cover. It's a whole subreddit: r/AlbumCovers (cover from this post).
People join by typing a title, which gets laid over the cover. Vote for the best one.
Start with one squiggle. Finish the picture by adding a squiggle of your own.
People join by adding their squiggle. Everyone's lines stack into one drawing, or each person turns the same starting squiggle into something different.
Record one clip, for example yourself saying a British insult. Everyone else records their own take on the same line. Example on r/SipsTea.
People join by recording their best British impression of that insult, shown next to the original.
Cat meets watermelon. Cat eats watermelon. Cat becomes watermelon.
People join by building their answer: feed the cat, a slider from cat to melon, a "what did you eat today" version.
Nothing matches. Try another word, or hit Surprise me.