The Bowery Boys Meet the Monsters may not be the best of the "Bowery Boys" series, but it was unquestionably the most profitable. It all begins when Slip (Leo Gorcey) and Sach (Huntz Hall) try to gain permission to use a local vacant lot for baseball games. The boys make a trip to the mansion of the lot's owners, the sinister Gravesend family. It soon develops that all the Gravesends are looney, and none loonier than mad scientists Derek (John Dehner) and Anton (Lloyd Corrigan). Derek wants to transfer Sach's brain (what there is of it) to the body of a gorilla, while Anton wants to use Sach's graymatter for his robot. Meanwhile, Amelia Gravesend (Ellen Corby) makes plans to feed Slip to her carnivorous plant. Along the way, Sach is periodically transformed into a hideous beast, terrifying one and all, including his would-be rescuers Louie (Bernard Gorcey), Butch (Bennie Bartlett) and Chuck (David Condon). There isn't a single gag or situation in Bowery Boys Meet the Monsters that wasn't used earlier by the Three Stooges or Abbott & Costello, but that doesn't make the film any less hilarious.
~ Hal Erickson, All Movie Guide