One of my favourite scenes in a sitcom is from The Fall And Rise Of Reginald Perrin: "Why are lions?" "Why are lions what, dear?" "Why are lions lions?" "Because they come from other lions." "Why aren't lions ants?" etc. Perfect "kid conversation" :D But that first line on its own is particularly great. "Why are lions?" I love it. On a tangential note, Bentley Rhythm Ace named one of their album tracks "Why Is A Frog Too ..?", which has similar energy.