My daughter “cleaned” my couch with vaseline once.
My brother (when he was three) cleaned the old yellowed keys on our piano with ajax and water so when you depressed the key, you got no sound and the key wouldn’t come back up.
He also tried to take a chair down to the basement (he was somewhat older at the time) and since he couldn’t get it through the door, he cut about an inch off each of the legs.
He’s a minister today. They just have to keep him away from the candles.