I'd say it's a three-way tie for favorites: 1, 4, and 6. Actually, they're the only seasons I like. I'd put 2 in my favorites if it weren't for the episodes where Buster was away.

Here's why I like them so much:

1. Lots of similarities between D.W. and Brain and possible allusions to sitcoms.

2. Very few dream sequences.

3. Many of the episodes have satisfying endings.

4. Lots of funny quotes.

5. Original plots for Arthur.

My least favorites: 5, 8, 10, 12.