He is a balding man with a small beard and his remaining red hair tied in a pony tail. He also has a hairy back, something he is not exactly proud of. He lives in a 1960's model van with peace symbols painted on it, and is usually parked somewhere in the neighborhood. He does not seem to have his own house. He wears a yellow shirt with a green patterned border and striped green pants, and he also plays the mandolin. His name Birkenbake appears to be a portmanteau of "birkenstock," a type of sandal stereotypically worn by hippies, and "bake," which is slang for smoking marijuana (since smoof is a parody of hemp a.k.a. marijuana).
Mr. Birkenbake acts and looks like a stereotypical hippie. He speaks of something called "smoof" and has many paraphernalia related to this substance. He also speaks in a very hippie-like manner and encourages his students to "fight the power". He does not get along well with Mr. Crocker.
His only major role in the series in the episode, "The Big Scoop!", where he tells Chester and A.J. that a story about his back hair was not acceptable news material and that he would cut them from the newspaper unless they gave him an exciting story. Later, after Chester and A.J. refuse to print a fabricated news story about Timmy Turner, Mr. Birkenbake forgave them and let them stay on the newspaper for doing that. He told them that being truthful was the most important thing about journalism and that it is better to write a boring truth than an exciting lie. He then told them to go find another story and Chester and A.J. promise to him that their next story will be exciting and truthful. The said story however was about them breaking into the permanent record room and Principal Waxelplax gave them detention upon finding this out.
He appeared at the front of the Turner's House in "Genie Meanie Minie Mo" selling various smoof-related items in a "garage sale without a garage" out of the back of his van. Among these items was a magic lava lamp which housed Norm the Genie. He also shows annoyance toward Mr. Crocker in this episode, remarking both to Timmy that he does not make "Crocker money", and to Crocker that he is a puppet of the military industrial complex or "The Man", although he quickly warms up to Crocker when he learns he is a potential costumer. Mr. Birkenbake also tells Timmy that "The Man" is the reason why he has never heard of Smoof.