Yellow Bus Riddle

Okay, so listen up, buttercup. This here joke is funny 'cause it's dark. You got this innocent image of a yellow thing, then BAM! It sinks a bus full of kids. It's funny because it's unexpected and morbid, kinda like your last attempt at cooking, which I heard ended with the fire department visiting. Don't feel bad, happens to the best of us... especially those who think boiling water is a culinary challenge.