Mr. Bergstrom took over for Ms. Hoover after she believed she had Lyme Disease and Lisa immediately took to him because he was the kind of male role model she needed in her life. However, after Ms. Hoover returned, he had to leave Springfield. A distraught Lisa ran to stop him, and Mr. Bergstrom gave her a note saying "You are Lisa Simpson". He then leaves for an unknown destination, never to be seen again[1].
When Lisa was sad because Maggie was smarter that her, Marge gave Lisa a paper that said "You are Lisa Simpson" and then Lisa says, "I already have one of those," referring to Mr. Bergstrom's note[2].
He, like his voice actor, Dustin Hoffman, is Jewish. He is an artistic, liberal teacher who tries to inspire his students, even though that means some will make fun of him, by drawing a picture of him with his guitar and naming him "The Singing Dork". Instead of being offended by this, however, he laughs and asks Lisa if he may keep it. Lisa says she did not draw it, although his praise of the art makes her wish she did. Mr. Bergstrom also encourages the students to patronize the Springfield Museum of Natural History, as it will soon be going bankrupt. This inspires Lisa to visit, and Homer is grudgingly made to chaperone her. Mr. Bergstrom encourages Homer to think more highly of himself, for he is the only man in the world who is Lisa's father.
Mr. Bergstrom has no immediate romantic interests and cares more for his students. This is made evident by his quote, "I'm sorry Mrs. Krabappel, you're very nice, but it's the children I love".
Oddly, the surname "Bergstrom" is Swedish, not Jewish.