Big Wolf on Campus (1999)

S1E16 Time and Again

A stranger offers Merton a watch capable of reversing time at will, but there’s a steep price: each use costs him a piece of his intelligence. At first, Merton eagerly exploits the watch for personal gain, undoing mistakes and reliving moments. However, with every rewind, he loses more knowledge and cognitive function. His mind rapidly deteriorates, stripping away memories and reasoning until he regresses to the mental state of an infant, helpless and unaware of the power he once wielded.