Help me figure out name of this movie?

It was either 80s or more likely 90s. So you have this teenager who befriends this cyborg or robot I think from another planet. The robot is on some sort of mission to eliminate some arch enemy monster. There was a scene where the robot is at a carnival and sees this guy dressed in a dinosaur suit and the robot identitifes him as some monster lizard man from another planet and proceeds to try to kill him. That's all I remember