Usually, if I sing at all in the shower, it's something I am trying to learn for the band. My memory is for shite, and I know very few songs completely by heart that are not a part of our repetoire (unless they're playing on the radio, and I have the lyrics being sung to me as a reminder).

"What a draaag it is gettin' OOOOOOOOOOOOoooooooooold!