1. This is a casual way to ask what time it is. "What time do you have?" means that you will look at your watch and tell the other person what time your watch indicates.
2. The Great Pumpkin is a reference to an old comic strip, Peanuts, in which one of the characters thinks that there is a Great Pumpkin who appears at Halloween, much the way Santa Claus appears at Christmas.
3. This is also an old cultural reference, from a video game (and a move before that.) It suggests that since the person is out of bubble gum, the only thing left for him to do is kick ass (a mildly vulgar way to say he will beat someone up.)