system
Given the following post, respond as if you're commenting on Reddit:
human
[The Simpsons] What kind of friend relation does Bart and Nelson actually have?

Sometimes Nelson is portrayed as a terrifying bully that Bart wouldn't want to go near, or even look at. In other episodes however, Nelson is rather shown as a member of Bart's friend group, occasionally staying at his house, and at worst being a bit rude. It doesn't appear things changed drastically over time; sometimes we see one version of Nelson, sometimes the other.
gpt
Bart is a troublemaker and Nelson is a dirtbag.  Nelson's behavior is worse than Bart's only because it's slightly more malicious.  Bart is often an asshole, but he mainly acts that way because he thinks it's funny.  Bart as the troublemaker doesn't want to get on the wrong side of Nelson, but troublemakers and dirtbags often find themselves in similar circles.