The Fairly OddParents (2001)

S8E11 Lights Out

After sharing a spooky tale with Poof, Timmy finds himself unable to sleep due to the baby's incessant crying. In desperation, he wishes for a twelve-hour stretch without light. However, Timmy is unaware that keeping his fairy godparents in darkness for more than eight hours transforms them into "Scary Fairies," turning them against him.