Abomasum

That's really difficult to answer. I loved Magilla, but I don't think a two-week-long friendship between nine-year-olds could ever have the same status as a year-long friendship that lasted at least until age 12. On the other hand, I am not aware of Brittany ever doing anything selfless for Delia that would have made me think she cares about her at all - not that I would consider this a crucial factor in defining friendship among children, being that 12/13 is not an age where social skills have reached an adult level of sophistication in any way, shape, or form. Brittany was a brat, but Magilla simply wasn't around long enough to reach friendship status - so I'll have to go with Brittany. I can at least believe that a kind-hearted person and good friend to Delia would have emerged from that cocoon at some point during puberty.

If you had to rewrite season four without one secondary character - would you get rid of Reed or Jake?