Even a person who never watched The Simpsons before, would enjoy greatly this one, even without knowing the characters as well as the regulars.
This episode is a truly rare pearl in a sea of bad episodes. I don't know how about others, but for me somewhere in the early 00's - The Simpsons stopped being my most favorite cartoon time and became just another one.
This episode reminds me of the good days, when you weren't sure you would end up disappointed after watching a new episode.
Bart is being Bart which is ALWAYS GOOD, but the real surprise is Martin, who gets darker just in the (very) unexpected good way.
Even Lisa's interaction with Marge and Homer was fun. Lately on the Simpsons, the side story is usually dull and the humor is dry, but this episode is almost-perfect, and certainly worth watching with a big smile.