Do you get Slylock Fox in your paper? We get it on Sundays. Now on the full understanding that the cartoon is for kids, and I should know after years of reading it that its logic is often flawed:
Well, my answer was "There are no ringed planets in the vicinity of the Moon/Earth system!"
However, the actual answer "sound can't travel in a vacuum", IMHO is moot considering they have already asked us to ignore the lack of spacesuits.
Um... and while I'm dissecting the cartoon, how are the ducks and the rabbit watching the movie with both of their eyes on our side of their heads? :D
Just my two cents.