Boo-boo keys is an inanimate object that only appears in the episode "Bubble Buddy."
Boo-boo keys are four of Harold's gold keys all locked together in a ring.
Role in episode
It appears when the citizens of Bikini Bottom are about to pop Bubble Buddy. SpongeBob tells the people that Bubble Buddy is his friend and asks the town if they have ever had a close friend. From there, citizens start bringing up material possessions that they consider friends, including Harold, who brings up his boo-boo keys.