Oh yeah, the Mr. Rogers episode was a classic. Really great message he gave to Arthur too about how real friends don't make fun of real friends, because Arthur was so worried that if the other kids in class found out Mr. Rogers was staying with them, they'd tease him for "being baby" (as kids are after Grade 2 if they incorporate such things into a conversation); and even in the end, they didn't make fun of him, but rather asked him if he did the same things he does on TV (take off his shoes, put on his sweaters, etc).
That also reminds me of that episode with the Teletubby-esque ducks that Arthur got hooked on because bright happy colors, and soothing music and absurdity of the whole show was eye-catching, and pretty soon the whole school was watching, despite it being a "baby show". But then again, that's how the Teletubbies were in real life - I was in Grade 3 when Teletubbies hit PBS, and even though it was targetted at little tykes, everyone in my class was talking about it... because it really did have that affect on us - the bright colors, the funny sounds, the soothing music... it was almost hypnotic... kind of like what Pufnstuf and most other Krofft shows did for college kids and adults back in the 70s.