Say "Nobita is Smart" Again! is an episode from the Doraemon 2005 anime. This episode is called Attaboy, Noby! in the U.S. English version/dub.
Doraemon shows Noby a gadget that can rewind time, and Noby uses it to repeatedly replay a compliment he received from his teacher, Mr. S. The boys end up using it to retrieve a necklace Big G got for his mother's birthday.