In a story arc from October 27th to November 4th of 1988, Calvin and each of the kids in his 1st-grade class were assigned to do a scientific report (complete with a scientific illustration) on a specific animal -- Susie Derkins was assigned to do her report on elephants while Calvin was assigned to do his report on bats.
Calvin obviously had no interest in doing the project (at one point, he called Susie and tried getting her to do basically all the work for him). The only "fact" he could think of was that bats are bugs (they're mammals), despite Susie and the rest of their classmates telling him otherwise. Since he didn't bother doing any actual research for the project, he opted for a dramatic, sensationalistic speech highlighting the terrifying aspects of bats.
Calvin, of course, fails the assignment, since it was obvious to the teacher that he did no research for it -- Miss Wormwood also criticized the illustration Calvin drew for it, apparently claiming, "Your 'scientific illustration' looks like you just traced the Batman-logo and added fangs."