Baby Stewie

Quagmire cannot drink while on medication, so the families go to an escape room instead, where Brian has Stewie solve the puzzles and takes the credit himself. Brian then shows Stewie a video of Chris solving a Rubik's Cube, telling him that Chris was clever as a baby and lost it at puberty, and that the same fate awaits Stewie. Stewie builds a machine to alter his own DNA, which leaves him an ordinary infant. Brian tries to reverse the process, and Stewie comes out rearranged as a monster. Peter has taped over Splice, so Brian travels back in time to the moment before the machine was finished and admits the video was a prank, played backwards from Chris eating the cube. Stewie's revenge is an order to drown his future self and put the timeline right.