Landing lag glitch
The landing lag glitch, also referred to as recovery carryover lag or RCO lag, is a glitch in Super Smash Bros. Brawl, Super Smash Bros. 4 and Super Smash Bros. Ultimate that causes certain special moves (usually ones that place the user into a helpless state) to have their landing lag carried over into a normal landing animation the next time they land. If the user grabs a ledge (in Brawl only) or gets hit after using a given move (in all games), once they land on the ground, they suffer much greater landing lag than what they would normally get (usually the same amount they would have gotten if they landed in a helpless state).
In Super Smash Bros. Brawl
In Super Smash Bros. Brawl, the glitch is activated once the player grabs a ledge or if they get hit out of a special move which activates the glitch. Most moves which are affected by the glitch are ones which put an opponent into a helpless although not all moves which cause helplessness cause the glitch and there are a couple of moves which trigger the glitch despite not putting the opponent in a helpless state (such as Kirby’s Hammer and Stone).
The only way a player can avoid the glitch is by using the landing lag from an aerial to override the RCO lag, (though with 35-40% more landing lag than would usually get for landing with that aerial). The player has to land while the aerial has landing lag. If the player auto-cancels the aerial, they will get RCO lag. Preferably, one would use an aerial with lag to partially override the glitch, but still suffer more lag than the aerial would normally provide.
Characters affected by the glitch
Except for Donkey Kong and Bowser, who get no additional landing lag from a soft landing, all characters listed have 15 frames for soft landing. Hard landing values are listed below.
In Super Smash Bros. 4
In Super Smash Bros. 4, the glitch no longer occurs after grabbing a ledge (with grabbing the edge flat out eliminating the glitch if it is active), which makes the glitch less prevalent and detrimental than in Brawl. The glitch does still occur if a player is hit out of their special moves however and multiple newcomers suffer from the glitch, in addition to many returning characters who already suffered from it. Because the glitch now only occurs when the player gets hit, the player will always go into their hard landing lag animation, unless they use a special move to land/carryover the RCO and then jump to get their soft landing (which will give them soft RCO lag).
Captain Falcon, Ganondorf, and Zero Suit Samus also remain affected by RCO lag after they connect with Falcon Dive, Dark Dive, or Flip Jump respectively and land on a platform. Any aerial used in an attempt to override the RCO lag will also experience increased landing lag, like in Brawl. However in some rare cases, such as Captain Falcon's up aerial, the landing lag received can actually be slightly less than the RCO lag they would have received otherwise. Some moves, particularly multi-hitting electric moves like Mewtwo's neutral aerial or Pikachu's forward aerial, induce extra landing lag on the character they hit if they end prematurely.
In Super Smash Bros. Ultimate
In Super Smash Bros. Ultimate, RCO lag has been removed for most special moves, making in even less common than in the previous game. However, there are still a few special moves which still suffer from the glitch (including Dolphin Slash, Blazer and Extreme Speed) and for these few moves which still have RCO lag, the glitch functions like in did in the previous game.