Calvin's Sandwiches are very specific(as shown in the picture). The sandwich has to be like this:
- 1.Chunky peanut butter only.
- 2.Open faced.
- 3.No jelly of any kind.
- 4. Normal bread, no "weird" grain breads.
- 5. Cut it diagonally.
The humor comes from this strip because Calvin's Mom did exactly all the things she wasn't supposed to.