I just did the first November adventure CG. It started with Bloo telling you to go find out why Wilt seems so down. When you talk to him he merely says he's down about the upcoming reunion. You go back to Bloo and he has you fetch his file, and what it says is that Wilt has no creator, that he was found as a "stray". Bloo has you go talk to Mr H to see if you can get more info from him, and Bloo gets in trouble for it and vows revenge on Mr H. So that may well be what happens in GWH, that everyone assumes his creator won't show because he was a "stray" but Wilt remembers his creator and goes out looking.
Anyways, here are all the new characters I've found:
A creepy tree friend;
Peanut Butter!
Chester;
A book friend;
And Red.
He is SO cute when he hops around.