have kangaroos in (one's)/the top paddock
To act, think, or behave in an eccentric, foolish, or nonsensical manner; to be insane. Primarily heard in Australia. Tommy must have kangaroos in the top paddock if he thinks he can convince Mom to let him get a tattoo for his birthday. There's an old lady who stands on the corner yelling at strangers all day. I think she might have kangaroos in her top paddock.
have kangaroos in the (or your) top paddock
be mad or eccentric. Australian informal 1985 Peter Carey Illywacker ‘And he was a big man too, and possibly slow-witted.’ ‘Leichhardt?’ ‘No, Bourke…He had kangaroos in his top paddock.’