I like making my own teams, they are comfy and easy to wear!
/end obvious lie.
I usually make my own teams because I can, and I like to include gimmics usually (like Seviper in NU!) However, I admit, I've stolen a team or two in the past. In fact, although I hardly ever are on the normal server of Shoddy nowadays (prefering CAP), whenever I go to play normal OU, I have been using CCAT #1 (the team with Heracross). Granted, I was one of the bigger contributors to that (in my mind), so it doesn't really count, but still.
And back in DP, weren't most stall teams essentially copies of ObiStall? Correct me if I'm wrong, but I think they generally were.