- You may be looking for the companion of the First and Second Doctors.
When he saw the Doctor's TARDIS appear out of thin air, he wanted to obtain it for the circus. He stole the TARDIS key from the Doctor and broke into the TARDIS. He accidentally dematerialised and landed it a few metres away, near the railroad. This act inadvertently lead to the death of Jumbo. (AUDIO: The Wondrous Box)