Helper dog

1) A dog trained to help humans with various tasks like hunting ducks, finding hidden cocaine, herding sheep, etc.
2) By extension, a dog with no special training trying to help humans with some task beyond its capabilities or understanding (such as car repair or calculus), but mostly looking confused and getting in the way.
3) By extension, a human doing the same thing.

“Don’t just stand there like a helper dog, go do something useful!”

Garbage sauce

The small packets of sauce, usually plum sauce but possibly chili sauce or soy sauce, included by the handful when ordering Chinese takeout or delivery. So named because no one wants them, at least not in the quantities supplied, and are thrown directly in the garbage unopened.

“I think they forgot your beef and broccoli— all that’s left in the bag is a couple extra chopsticks and some packets of garbage sauce.”