The Secret Keeper Dog

Nobita uses Doraemon's Secret Keeper Dog to cover up breaking his dad's pen and getting another zero on his test. He later uses the gadget to cover up his friends secrets (with a lot coming from Gian), which causes the dog to expel them out in the middle of the night. As a result, Tamako and Nobisuke wake Nobita up to scold him for the broken pen and test paper.