So I've been working my way through the episodes and am currently on the 7th season. Since I watched this show a lot when it was still on the (US) air, I can't help but be irked by not being able to find this:

In one of the episodes, Malcolm, Reese, and Dewey have a babysitter. This is nothing new, but I remember that in the episode, they phoned Francis. He was surprised to find that the girl, who had apparently been overweight when Francis was in public school, had become significantly more attractive in the intervening period. I forget how important this was to the episode, but I also forget what episode it was. Anyone know which episode this is from?