He is very much like the Arbiter, but prefers to read (mostly with Cortana), and doesn't seem to use foul language at all (only mildly cursing when fighting for his life when Chief tried to kill him).
Master Chief thinks of him as a "gigantec pusy (gigantic pussy)", which, surprisingly, is true, such as in the Movie, when Chief pulled a not-too-scary prank, Todd ran away, screaming effeminately at the top of his lungs. He is somewhat smaller than the Chief. Chief attempted to kill him and Travis in Episode 12. Also, Todd appears to be easily fooled, as shown in Episode 12 when, while trying to kill him, Chief tricked him into turning around, saying "HOLEH MOTHR OF GOD L@@K OTU ITS TEH COVERNINT (Holy Mother of God! Look out! It's the Covenant!)" while pointing behind Todd. Todd turns around, opening an opportunity for Chief to smash him off with a frying pan, then grabbing the "ROFLKNIEF".
He was removed in episode 12.
Later, it is revealed that he, Travis and Cortana were abducted months ago by an alien called Xanthor, who then "anally raped them and then eated them alive, while he throwed Cortana into a nearby sun". (The entire scene was a shoddy attempt on DigitalPh33r's part to explain their disappearance).