Mister Stewart

Mr. Stewart is a character that appears in the anime series Sonic X and its comic series published by Archie Comics. He is a human government agent who worked undercover as a school teacher at Station Square Elementary School, his assignment being to watch Sonic the Hedgehog and his friends by the President under the code name "Chalkboard Charlie". After disregarding his superiors' orders, however, Stewart got moved to other assignments which would intertwine with Sonic and his friends' future adventures.

(Source: Sonic Wiki Zone)