J. Brennan Smith was put into a fat suit while playing Elmer.
Willie is surprised to see the size of Elmer's sandwich. When Harriet goes on a trip, Nels prepares food for Willie but he never seem to have enough to eat. He eats his portion of food and sometimes his father's. And in season 8 the Reincarnation of Nellie, Willie makes a sandwich so big he has to use a pan to hit it in order to flatten so he could eat it.
This is another story in the series about a boy named Elmer who is teased and bullied at school, who in the end gives a touching monologue about friendship and kindness. The other one is The Election (1977) from season three.
This is the fourth and last episode where obesity is the topic. The first one was the Man inside and then the next one was Annabelle and Mrs. Olsen in To see the light.