I've been playing the game for a while now, it's just so awesome!
My first custom level was a T-rex with a top hat and a saddle. I used the mind-control device to let me ride him and kill the zombies
A great surprise is to summon two Maxwell clones and a fake Starite. They will steal the Starite from each other going "yoink!" each time!
The puzzle levels are an interesting set-up of scenarios, most of which are pretty clever. The action sequences are less fun, but are still good in their own way.
I hope some interesting levels are created quite soon.
NOTE: No copyrighted characters are in this game.
PS Here's a funny Slig Scribblenauts picture that someone else created