Bill is Herbert's pet dinosaur who is faithfully loyal to him. Bill is more intelligent than Rookie and wants to secretly eat the world, that is why he is drinking lava and sody pop so much, so he will get fat.
Herbert decided to enslave dinosaurs after the idea of enslaving Klutzy and Puffles, but one problem: He was too fat to enter the time trekker. He was so big that the strange machine couldn't let him in. So he enplanted a fattening device that made the machine have wide space like the TARDIS. Apparently this effected a fat purple Tyrannosaurus rex, and when they both entered the time machine, they thought they were both beautiful.
Soon after Bill ate Aunt Arctic even though an idiot Stegosaurus told her it wouldn't happen.