[Snerk.] What, you think you know him better than I do now? He'll be bouncin' on his heels the second he sees you, ready to drag you around and show off everything he knows about the place. Betcha he's got speeches ready and everything.

[Dipper is absolutely a showoff. To be honest, Stan doesn't actually think it's a bad quality - he's mostly just jealous because Dipper clearly has a favorite Grunkle and it isn't him.]