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An airplane and a helicopter can be found amongst the game's ending sprites. They never show up in any endings, but otherwise work perfectly and can be made to appear via hacking.
Contributed by MeleeWaluigi
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Playing game B on speed 9 and reaching height 5 will provide a sequence of Nintendo characters celebrating. These characters include Mario, Luigi, Peach, and Bowser from Super Mario Bros., Donkey Kong, Link from the Legend of Zelda, Pit from Kid Icarus and Samus from Metroid.
Contributed by gamemaster1991
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Hacking the game reveals an unfinished, but playable two-player competitive mode in the game's code.
Contributed by Antwan