Trying to ruin your day or moment by doing something childish, petty or immature - like some did in kindergarden.
Similar but to "bust your chops", "break your balls", etc but with the added element of doing something childish or immature.
"My neighbor is a ballbuster. He purposely ran his dog through my flowers because I wouldn't lend him my lawnmower."
"Don't worry he's just trying to break your crayons."