Mega Man 4/YMMV


 * Anti-Climax Boss: Dr. Cossack. Exemplified by the fact that you don't need to empty his energy bar all the way before the fight suddenly ends.
 * Base Breaker: There are two major camps of Mega Man fans: those who consider either Mega Man 3 or 4 to be the last great NES Mega Man (the latter in no small part due to the ability to charge your Mega Buster, which would become a mainstay mechanic for nearly the entire franchise).
 * Breather Boss: Toad Man, since he can be looped into an infinite where he does nothing but jump. Pharaoh Man too if you use his weakness (he becomes a sitting duck), and Bright Man if you know how to stop him from using Flash Stopper (though he's still more challenging than the former two).
 * Contested Sequel: While few will call Mega Man 4 a bad game, when its predecessors are considered the best games in the series (and often the best games on the NES), it can't help but fall into this territory.
 * Fanon: Fans love taking Dr. Cossack's Glorious Mother Russia aspects and cranking them Up to 11. The fact that his Supervillain Lair resembles features of the Saint Basil's Cathedral doesn't help.
 * Fanon Discontinuity: Some hardcore fans like to consider Mega Man 3 the true final game of the classic Mega Man series, preferring to assume Dr. Wily died at the end of 3 and ignoring everything from 4 onwards. Some less hardcore fans like to consider the same of Mega Man 6, and ignore everything from Mega Man 7 onwards, while still others ignore only 7, 8 and & Bass, considering only the classic NES style games (1-6, and 9 and 10) to be canon.
 * Good Bad Bugs:
 * When one uses the Flash Stopper, certain enemies that would normally be shielded from the Mega Buster lose that invulnerability. This means one can shoot Shield Attackers in their shielded side and destroy Skeleton Joes that are otherwise impervious to anything other than a charged Mega Buster/Pharaoh Shot attack.
 * When fighting Tako Trash in Wily Castle 2, one can use the Drill Bomb to destroy the boss's hatboxes, allowing Mega Man to walk behind it without taking Collision Damage, shoot it from behind, and be completely safe from its fireballs and bombs.
 * If the player leaves the room Eddie appears in before he teleports away, and without picking up the power-up he gives out, then Eddie will respawn when the player returns and revert back to walking towards them and giving them a power-up. Since the power-up given is always random, it gives the player an unlimited number of do-overs if they get an undesirable power-up (the only exception being rooms where Mega Man enters from the ceiling and can't leave and re-enter the room quickly). This bug also works in Mega Man 5 and Mega Man 6.
 * It Was His Sled: It's almost common knowledge by now that Dr. Cossack isn't the real villain.