Revealing mistake: When Bumblebee is knocked onto his side, Ratchet kneels down to shove him back onto his wheels. The only problem is that when Bumblebee drives away, the animators forgot to add Ratchet's leg (that was previously obscured) into the frame.
Continuity mistake: Optimus Prime, whose primary color is red, when being tied to a rock alongside his troops during the episode's climax, turns blue for a second.
Answer: This was actually one of many errors in Transformers, the Constructicons MUST have been built on Cybertron, the only transformers genuinely built on earth were the dinobots, reason being Vector Sigma has to give personalities to each and every robot, else they end up like the dinobots, very simple and dumb. For reference watch the episode "The Key to Vector Sigma" which introduces the Stunticons and Arielbots - both Megatron and Optimus Prime have to go to Vector Sigma to get decent personality traits installed, prior to this the new robots are controlled by remote controllers and have no AI.