Well, I think Mr. Morris was a continuity error on the part of the animators. I almost wonder if they either forgot the episode entirely, or they never redesigned a new Janitor character, thus using the old one as a BG character. I've seen new episodes where he is indeed in the background, but I don't think I've seen any where he's mentioned by name. Unless there is one, I can't fault the writers. So, again, it could just be an animation error.I know that, and we don't even know for sure just yet if Mrs. MacGrady is going to die, I was just saying in the event she might, knowing the show they might bring her back like they did Mr. Morris when he was supposed to have moved away after he broke his ankle during the fire at school; and while I certainly see your point about sending the heavy message across to the kiddies, something about this episode (the timing of it this far into the series and all) to me just screams how short they are on ideas for the show.
As for MacGrady... well, I don't see the writers having her die at all, just dealing with the illness. The brilliant idea of having Lance Armstrong guest voice shows that they intend to spread the message that it isn't exactly the end. Similar to Kami from that South African Sesame Street co-production. And I think I like that better than just killing a character off. It shows that there are survivors, and people who live for a long time dealing with it... not that it's an instant kill or a fatal disease. And knowing MacGrady, she's strong enough to beat it.