Stupid is the puppy Bloo named from "Who Let the Dogs In?"
And a lot of these are friends we've only heard mentioned, but don't know who they are. As for the Mojo Jojo look-a-like from the pilot, I think we've been speculating the "Wojo" from the good-bye card everyone signed for Mac in the finale is him, but it's not official. Which makes me wonder, if listed are friends whose names we know but whose faces we don't, should we list friends who signed the card who we also have no idea who they are?
I also added to the list just now Frank, Jo and Phil (the unicorns), as I noticed they were not previously listed.