The title given to the last pizza served at "all you can eat" pizza. It has a ginormous amount of cheese on it, but very little sauce.
The purpose of the Cheeseosaurus Rex is to get people to stop eating pizza. The thought behind this is that cheese fills people up so they will not be able to order any more pizza.
Scott: let's have another pizza; our eigth one.
Rob: SHIT MAN! here comes the cheeseosaurus rex!
Kenny: wtf?
Rob: that's when they put a crapload of cheese on the pie to make you stop eating.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.