Tanner was a very elitist character, demeaning different people on several occasions. During class he was seen picking on Elena when she wasn't paying attention to him, prompting Stefan to openly challenge and correct him on several occasions.
As the football coach of Mystic Falls High, Mr. Tanner appeared fair, he allowed Stefan to try out despite their tendency to butt heads in class and also let him on the team when he saw what a good player Stefan was. Before Stefan tries out, Mr. Tanner made a snide remark about asking Stefan who won the Superbowl a while back in the 1900s. Stefan started to answer, but stopped, looking at the expression on Tanner's face.
In the novels, Mr. Tanner is as European History teacher. Like his TV counterpart, he liked to question his students who weren't able to answer correctly. He was corrected and embarrassed by Stefan Salvatore on how Renaissance European youths behaved and lived their lives -- because he was born in that era.
At the hollow party he was killed by Stefan's brother Damon.
- See Also: Mr. Tanner (novel)
William is of Old German origin, and the meaning is "will helmet, protection".