Instructions
Examine the room carefully before you start moving. Take note of the TV button on the left and the pressure plate on the right. You will need to move between these locations quickly in order to defeat the boss.
Drop a TV onto the TV plate you noticed, then run to the right and up the train tracks going over the thinner pool.
Drop an Anvil onto the pressure plate near the mad doctor and the Beetleworx enemies.
Run back over the thinner pool and step on the second pressure plate you noted in the first step. This will cause a cutscene to start where a train comes out and crashes into the Mad Doctor's last remaining Beetleworx generator. This is all you need to do to defeat the Doctor.