doormouse
(noun)
1. The doormouse who floats out of a teapot in Alice In Wonderland with fireworks exploding around him while he sings. Quite trippy.
2. (Modern usage) Someone who is always singing randomly and badly. Often they sing any song, regardless of actual original tempo, quite slowly. They know they are singing badly, but they don't care. Can be cute at first, but often leads to fatal accidents, such as being strangled.
1. "Twinkle, twinkle, little, bat. How I wonder, what you're at. Up above the world you flyyy, like a tea-tray, in the skyyy."
2. Person 1:  Gooo askkk aliceeeee, ohhh sheee'ss teenn feett talllll....
Person 2: Shut up dude, you're such a doormouse.