not funny jokes

this morning my co-worker got out a book of kids jokes and started skimming thru it. the first couple kids started to arrive so she decided to try some of the jokes out on them. even the kids didn't find them funny. at one point she went to answer the phone and i picked up the book. the first one i read took me a minute to get:
q: what kind of biscuits can fly? a: plain biscuits.
(plane/plain for those of you as slow as me-- my excuse is that it was still early, my coffee hadn't kicked in).
a minute later the kid sitting next to me repeated the joke only when he said the punchline it was "flying biscuits." (he didn't quite get what made it a joke). a couple minutes later he repeated it again to a mom and a kid who just came in only this time it was "what kind of cookie can fly?....a flying cookie!" um.....yeah.
between him and another boy the "jokes" getting less and less joke-like as they sat there and made up their own for 5 or 10 minutes. i kept laughing when they'd tell me new jokes though, not cuz they were funny but because they were soooo random and didn't make any sense at all. example: why did the kinder cross the road? (what?!?) answer: because it got run over by ten hundred cows!!!! (huh?)