Don't Shoot the Message: This episode's message is that while it is okay to say no to people, that's no excuse for you to be rude to them. A good lesson in all, but both Sandy and Mr. Krabs come off as rude at the beginning of the episode through refusing to take no for an answer when SpongeBob says he can't do any favors for them when he and Patrick want to spend the day at Glove World, and through taking advantage of his Extreme Doormat status without caring about his feelings and they are both not called out for it. It's especially bad in Sandy's case considering that she knows better and even tells SpongeBob in the end that he's fine the way he is and doesn't need to change anything about himself. Also, because this episode only shows SpongeBob saying no to his friends through being rude to them due to his Abrasive Side, he is never portrayed in the right when he does say no to them.
Informed Wrongness: The Abrasive Side is entirely meant to be painted as a jerk with how he treats SpongeBob's friends, but calling out Sandy for using SpongeBob as a guinea pig without his consent and calling Mr. Krabs out for his cheapskate ways are both things he had every right to do. Mr. Krabs especially considering he told SpongeBob to work a seventeen hour extra shift which is considered overtime work, and yet the Abrasive Side is painted in the wrong for demanding Krabs to pay him overtime even though that's a fair trade if SpongeBob were to work overtime.
Strawman Has a Point: At first. Prior to becoming an outright antagonist, the Abrasive Side was treated as a big jerk for his treatment of SpongeBob's friends. While Patrick and Squidward didn't really do anything to deserve it, Sandy and Mr. Krabs did: Sandy tried to use SpongeBob as a guinea pig for one of her new inventions without even bothering to ask first (not to mention it was her taking advantage of him that got him to buy it in the first place), and calling Mr. Krabs out on his cheapness is hardly a bad thing.
Unintentionally Unsympathetic: Sandy. We're supposed to see her as teaching SpongeBob that he shouldn't be rude to people, but considering she took advantage of him at the beginning of the episode, it comes off more as her not being able to take no for an answer and makes her out to be a Hypocrite. As a result, the scene where the Abrasive Side causes her invention to make her head disappear is supposed to depict him as being in the wrong. It inadvertently looks like Sandy getting karma.
Earworm:
Broken Base: Viewers are directly split down the middle on the episode. Half really like the episode for its relatable topic of being unable to get a catchy song out of your head and admire how many visual gags there are, while the other half find it insufferable because of "Musical Doodle" alone and how much it's played over the course of the episode (which is likely the point).
