I was contacted by a non forum member on a quest to learn more about a Cartoon Network contest (likely UK only) that took place in 2005 called "Kazoo Us a Clue". Bloo would a play a song on his kazoo and kids would phone in with their guess of what the song was, and win some prizes. I personally have no memory of this but then it may have been UK exclusive.
Does anyone remember this contest?
Here is a thread about it.