The Mechasaurs are a trio of robotic prehistoric reptiless, most likely built by Chief Goppernopper. They are a robotic T-Rex, Triceratops and Pterrodactyl. The robot T-Rex first appears and beats up Mog Mog. It later appears with the pterrodactyl and triceratops due to the Chief gaining knowledge of computers and uploading pictures of the boys and Lily into their memory banks. The beasts then pursue the three protagonists back to the future where they take refuge in a warehouse. They then camoflague themselves by wearing bags on their heads and spraying their pictures onto buildlings, including the Goppernopper Tower. Lily then sprays a picture of the boys and her onto a barrel of explosives. Our heroes return to the past and the Mechasaurs are incinerated. The beasts' remains aren't recovered, but after the Goppernoppers were eliminated, they too also faded out of existence.