Calvin has a strong dislike for bees. He doesn't like it when they sting. During the early days of the strip, a bee would land on Calvin's back, which ended up stinging him when he moved (in one instant, a hornet landed on him instead). Whenever he spotted a nest of bees, he would always throw rocks at it, which of course resulted in making the bees angry.
In some cases, he would imagine the bees as being a larger-than-normal size. In one strip, he described a bee as the size of a Kaiser roll, with a stinger like a harpoon. In another, after throwing a rock at a bee nest, a gigantic, angry bee came out. Calvin tried to flee, but to no avail, as the bee eventually caught up with him and stung him. After that, he tried to explain about the "harpoon" stinger that "gored" him, and told his mother to call the National Guard to track the bee on radar.