She is Mr. Krabs's girlfriend. Some small, early examples of Puff's antagonism can be seen in the season one episodes "Scaredy Pants" and "Sleepy Time." In the former, Mrs. Puff spots SpongeBob while in her boat. SpongeBob has just been bullied, having been called "ScaredyPants" by his coworkers and strangers alike. Puff honks her horn to scare him, then laughs and calls him "ScaredyPants." SpongeBob responds, telling her to call him by his real last name. In "Sleepy Time," Mrs. Puff visits SpongeBob in a dream he is having about being able to drive. She takes his dream license and rips it to shreds, shouting, "Not even in your dreams, Mr. SquarePants!" This moment is a good example of Mrs. Puff committing an unnecessarily angry action towards SpongeBob.
Later episodes show Puff involved in other small antagonistic acts. In "Nautical Novice," Mrs. Puff is on a bus when she sees SpongeBob trying to catch up to her. She tells the bus driver to keep driving rather than stop for SpongeBob, despite the danger SpongeBob is in (he is running in the middle of the road). In "Boating Buddies," a temporarily-handicapped Squidward cannot pick up his pencil because of his bandages, rendering him unable to complete Mrs. Puff's test. Rather than supply Squidward an alternative assignment or more time, Mrs. Puff instantly fails him at the end of class, forcing Squidward to endure another week of sitting next to SpongeBob.
Some later episodes of the series show that Mrs. Puff has become increasingly violent, and she occasionally resorts to violence as a first. In "Growth Spout," Mrs. Puff hears rummaging in her garden and immediately grabs a blunt, crowbar-like instrument. She yells outside that she is not afraid to use the weapon. This can be seen as proof of Mrs. Puff's paranoia causing her to become entirely insane, even in areas of life that do not have to do with SpongeBob. In "SpongeBob LongPants," Mrs. Puff hears that another driving instructor has passed SpongeBob. She panics, saying that it is the "end of the world," then starts to lock her doors, bar her windows, and collect rations. She is last seen holding a large harpoon and wearing a war helmet. It is important to note that in the episode "Doing Time," Mrs. Puff tries to beg the police to not arrest SpongeBob, as he is "just a student driver" and she feels he does not deserve to be arrested. In the much later episode "Oral Report," however, her feelings on SpongeBob have notably progressed. When the police confront SpongeBob, she evilly laughs and tells SpongeBob: "Finally! The long arm of the law's caught up with you! I guess I won't be seeing you in my driver's education class for the next 5 to 10 years!" This quote exemplifies the difference between pre-movie Puff and her post-movie self.