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In a story arc from October 27th to November 4th of 1989, 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). So he asked Hobbes to help him out. The only "fact" Calvin and Hobbes could think of was that bats are bugs (they're mammals), despite Susie and the rest of their classmates telling Calvin 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. He even put his report in a "professional" clear plastic binder in hopes it would give him a good grade.

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."

On the way home from school, he (as usual) comes up with an excuse: another reason why he got a bad grade because Miss Wormwood wouldn't give him ANY credit for the clear plastic binder he put his report in (which, given its lackluster contents, was just as worthless).