Mrs. Puff

Mrs. Poppy Puff is a boating School Driving instructor who teaches students (including SpongeBob) at Mrs. Puff's Boating School. SpongeBob has attended the school ever since its opening, and has failed his final driving exam countless times, often injuring Mrs. Puff and/or damaging the school in the process. Mrs. Puff hates teaching SpongeBob more than anything in her ocean world.
SpongeBob SquarePants, Mrs. Puff's longest-standing student, is the bane of her existence. His distracting personality, reckless driving and inability to improve torment her to no end. SpongeBob has failed his driving test countless times, often sending Mrs. Puff to the hospital and causing immense property damage in the process. On multiple occasions, she has been sent to jail as a result of his actions. To make matters worse, SpongeBob has failed to come to terms with the reality that he cannot learn to drive properly, largely due to his boundless optimism. Due to this, she and Squidward Tentacles are on very good terms for good or evil, since SpongeBob is also Squidward's bane of existence, so she has someone to relate to. However, in comparison to Squidward, she is much kinder to SpongeBob (probably stemming from their teacher/student relationship); for example, while Squidward usually tells SpongeBob face-to-face that he hates him, Mrs. Puff has at least tried to hide her fury. Also, she has even acted nice to SpongeBob on some occasions, like in the episode Krusty Love, she showed no annoyance or anything negative to him, except when she screamed in horror when she thought they were doing the boating test, and the second time, when she's on her second date with Mr. Krabs, he states SpongeBob is helping him tonight, she says slightly worried, "Just a second. I need to go call my insurance agent."

Personality

Mrs. Puff is very paranoid and erratic, and has had a history of mental instability. In "No Free Rides", it is implied that she has had to move to another town and start a new life with a new name in the past. While this is mostly caused by SpongeBob's antics, it is possible that some of it is caused by loneliness she suffers from after her husband was killed by humans and made into a lamp.
At the beginning of the series, Mrs. Puff seemed to not be so optimistic towards SpongeBob and actually treated him like a close friend, save a few moments when SpongeBob crashed during the course. However, as the series has progressed, Mrs. Puff seems to have developed an intense hatred of him, and can even get a fit of mental instability by just looking at him. This could be because of the fact that SpongeBob becomes more troublesome as the series progresses, and has caused Mrs. Puff great trouble lately. Her thoughts and fear about SpongeBob cause her to think that she was giving SpongeBob a driving test even though they are not at school. This occasion happened at "Krusty Love."
In the episode "Doing Time" when Mrs. Puff, thinking she is about to die, says "Where did I go wrong?" The scene then cuts to a flashback of Mrs. Puff, presumably at the opening of her school, saying "...as long as a student is willing to learn, I shall never give up." Right after she says this, SpongeBob appears and introduces himself to her.
In the episode "Mrs. Puff, You're Fired", Mrs. Puff is fired by her boss, Mr. Fitz, who holds her responsible for SpongeBob's repeated failures. However, she is rehired at the end of the episode.