Patrick's Secret Box is a box that Patrick kept that contains a secret and is the main plot element in "The Secret Box." SpongeBob wanted to know the secret, but Patrick would not let him. One night SpongeBob tries to steal it to know the secret inside the box. Patrick catches him but lets him look inside. But the only thing seen inside was a "secret" string. But when SpongeBob left, Patrick reveals that the string could be pulled to reveal the secret compartment of his box, containing an embarrassing snapshot of SpongeBob at a Christmas party.
SpongeBob wanted to look inside, but Patrick said if he did, it would break their friendship forever. SpongeBob thought Patrick could have held diamonds, severed heads or a snapshot of him at a Christmas Party. SpongeBob became so desperate to look inside he decided to steal it from Patrick's rock and look. SpongeBob thought the box contained only a piece of string, but really when pulled, the string opened a secret compartment inside the box, revealing the actual item inside was an embarrassing snapshot of SpongeBob at the Christmas Party.