Remember those collabs?

I don't know if they were ever a big thing, but I did see them. I mean all of them. Both the ones were you worked on the same doll and the ones with multiple dolls in an image. I think I might have done the latter once. I always wanted to do something with someone else, it would be interesting to see how someone else could improve on what I do. Ah so few people around to do things these days...Did anyone else ever do those?