Role-playing games often use the question of who-shot-whom in a game of Cowboys and Indians to explain why they use die rolls to resolve those issues. They assume that most players aren't as fair-minded as Charlie Brown!
Calvin would not have let Shermy win like that. In fact, Watterson would have probably turned this into a Sunday strip, and have Calvin go to extravagant lengths to come up with reasons that Shermy could never have hit him with his ray gun. This is why Calvin was so popular with his non-tiger friends.
