This is a hilarious series of shorts that used to air as a part of "Wedgies", cartoons made to be aired during commercial breaks, on Cartoon Network and Boomerang.
The series followed Mr. Bixby who worked as a substitute teacher at a local school. He was assigned various different jobs by the short-tempered school principal when no other staff were available to take over. These jobs included substitute bus driver and substitute auto class teacher.
Little information is available on the shorts, so it is unknown if there was ever supposed to be a full series based on them. I think the character of Mr. Bixby showed great comedic potential, so it is a shame more was never done with him.
I highly recommend you check out the five shorts if you haven't done so already. My personal favorite is "Mr. Bixby as the Substitute Career Counselor".