Not a "bug", per se, but an easily (presumably) fixable inconsistency with Super Mario Bros. scoring. First of all, the stomp scoring sequence (which is correct in SMBC) is 100-200-400-500-800-1000-2000-4000-5000-8000-1up-1up... As correctly simulated in the game, walking into an already stunned Koopa shell gives you 400 points. However, if kick it from mid-air, the score you get is determined by how many enemies you hit before kicking it. Basically, it takes the score of the last enemy you hit, and goes three steps up from that. So, if you stomp on a Koopa and kick its shell without touching the ground, you'll get 100, then 500 points. If you stomp three Koopas in a row and kick the third one's shell without touching the ground, you'll get 100-200-400, then 1,000 points. If you happen to kick both the second and third Koopas' shells away before touching the ground, you'll get 100-200-400, then 1,000 from each of the shell hits. And lastly, if you jump on a Koopa, then jump on the shell to kick it without hitting anything first, you'll only get 400 points. EDIT: Here's a demonstration.
