This Koffing being released in the same year as M.U.G.E.N itself makes it the oldest known Pokémon character created for the engine, so the character's lack of moveset options and the inherently obvious bugs typically associated with DOS-era characters shouldn't come off as too much of a surprise. While Koffing is unable to perform basic actions like jumping, crouching or blocking, it has the benefit of permanent grab invulnerability.
Koffing is a two-button character that uses the (A) and (B) buttons to activate the majority of its four attacks, with Tackle instead using ; out of the rest of the four moves, Smog is split into two variants that use a single button press of either (A) or (B), Smoke Screen is used by pressing (A) and (B) simultaneously, and Self Destruct is a Hyper that requires more than simple button presses, necessitating a motion in conjunction with (A) to activate. There are only minor differences between the two Smog variants, with the (A) variant being the slightly quicker attack that travels upwards slightly and the (B) variant being the more damaging attack that travels in a straight line; however, the (A) variant is incredibly weak for not being that much faster than the (B) variant, which combined with the hitbox of the (B) variant persisting for longer, often renders the (A) variant as the less viable option in most circumstances.
Koffing is unable to either block an opponent's attacks or crouch, though the latter is generally irrelevant due to having no crouching attacks of its own and being unable to block an opponent's low attacks anyway; however, the character does have a few defensive capabilities to help protect itself, with the most prominent two being permanent grab invulnerability that forces an opponent into using either melee attacks or projectiles, and the ability to temporarily become invulnerable to projectiles by using Smoke Screen, though the effectiveness of said move is reduced by it merely being a defensive measure against projectiles and not aiding in the character's approach. All of the character's attacks have limited range, with Smoke Screen and Self Destruct requiring Koffing to be in point blank range of the opponent for the moves to hit, and while some of the range problem are minorly offset by very short startup times, they often don't compensate for an opponent being able to safely hit Koffing at a distance; another issue with Koffing's attacks is their inability to combo, which hampers the character's ability to rack up reasonable damage before an opponent can safely navigate to a safe distance.
Koffing suffers from an incredibly slow walking speed, which becomes a major problem when the character's incapability of either running or jumping is factored into the equation, as walking at this ponderous pace is the only way for the character to cover any ground; not helping Koffing's case in this regard are the aforementioned short ranges its attacks can reach to, effectively making the character mostly helpless against opponents with even the most basic zoning capabilities or those that are fast enough to employ hit-and-run tactics. Due to being a character created in the DOS-era, Koffing suffers from a major bug that can severely hinder the flow of battle and potentially put Koffing at a heavy disadvantage, as it is unable to get up from lying down if an attack that causes knockdown is used against it, and while it is possible to knock the character out of this predicament with an OTG attack, an opponent can just leave Koffing stuck in this state and wait until the time runs out if it doesn't have the Life lead.
Koffing not having a custom A.I. makes it resort to using M.U.G.E.N's default A.I., though owing to the simple nature of the character and its inability to block or jump, combined with its ludicrously slow walking speed and short ranged-attacks, it rarely poses any sort of offensive threat to a character that is capable of fighting back. What makes Koffing's A.I. awkward to fight is the liedown bug that is present within the character, as Koffing getting stuck when it gets knocked down requires an opponent to try and avoid using knockdown attacks if the match time is set to infinite and they don't have an OTG move to 'free' Koffing when it has the Life lead.
Hovering the mouse cursor over the Command Input icons will display text that refers to the inputs set in M.U.G.E.N's Key Config.
Icons encased in square brackets [ ] require the respective button(s) to be held down. Hovering the mouse cursor over the gap displays the hold duration if applicable.
* Deals 200 self-damage Leaves Koffing with 1 life remaining if Life if lower than or equal to 200 Uses 2000 Power
This character does not have any victory quotes, meaning it uses the screenpack's default.