Update on the T-Rex/Cupid Arrow freeze glitch:
It seems like ANYTHING that normally hates you that you hit with a cupid arrow will make the game freeze if you try to ride it through a time machine/teleporter. (Wow, what a broken ass sentence. Either way, you understand.)
My guess is that when it creates a new scene (when you go through the time machine), it has to remake all the objects on screen. When it does that, it resets their stats. Normally, you're not able to ride a T-Rex, so when it goes through the time machine, it resets all of its stats, meaning it gets angry again. Meanwhile, Maxwell's object is in a state of riding a T-Rex, which the T-Rex object no longer allows. Since the game contradicts itself, it crashes.
This is a shame, too, because as a programmer, there are really simple fixes for this. Alas, in a game like Scribblenauts, not everything can be tested.