Capsule

Megavitamins come in 6 different color combinations of red, blue, or yellow (Red+red, blue+blue, yellow+yellow, red+blue, yellow+blue, red+yellow). Dr. Mario uses the megavitamins to destroy Viruses, in the game Dr. Mario. Interestingly, in Japanese, Megavitamins are simply called カプセル; Capsules.

In Super Smash Bros. Melee, Dr. Mario's neutral B attack makes him shoot Megavitamins. They act the same as Mario's Fireball move, except that the Megavitamins are more powerful. In fact, they are one of the strongest fast-moving projectile in the game. They also bounce in a different path, and make a different noise when it hits. There's also a trophy of Dr. Mario shooting Megavitamins and one of the vitamins themselves. Kirby is also able to use the Megavitamins if he copies Dr. Mario's powers.

Megavitamins also seem to have a transform purpose, when Dr. Mario or Wario ate them, they would transform into Metal Mario and Vampire Wario, respectively. This may be an aftermath of the Megavitamins attempting to destroy them like it destroys Viruses. In Super Smash Bros. Brawl they appear as stickers.

Trophy Information
''Megavitamins come in six color combinations of red, blue, and yellow. Dr. Mario uses these capsules by tossing them into contaminated bottle to destroy viruses. The origin of these wonder pills is a mystery, but the most likely theory is that they're the result of Dr. Mario's lifelong efforts to find a cure for the common cold.''