Sheep, drum, and snake

Alright, listen up, buttercup. This joke is a pun. A sheep says "Baa", a drum goes "dumm" (or "drum"), and a snake goes "tsss". Put 'em together, and it sounds like "badum tss", which is the noise a drum makes after someone tells a joke, which signals that the joke is over! And you didn't get it. I bet you also think Nickelback is good.