Why can't he get it through his 'thick head' that I don't like him? [=why can't he understand that I don't like him?]
Presidential candidates are 'thick on the ground' this year. [=there are a lot of presidential candidates this year]
They were (as) 'thick as thieves' [=very close and secretive] for weeks, which made us wonder what they were doing.
(..) Don't talk to him like that. Here. You okay? Thank you. Um... How's your head? I mean, It's fine. Ah... I'm good. Ha. I've got a thick skull. I don't have a skull...Or bones. So... So Now what? Now what? Now what?! Oooh! What am I gonna do? (..)2013 Frozen