Quick Attack cancel
Quick Attack Canceling, abbreviated as QAC and also known as QuACking, is a technique usable by Pikachu in Super Smash Bros. Brawl. It involves using Quick Attack into the ground and jumping (or dropping if aimed into a soft platform) to cancel the lag at the end of the momentum, allowing Pikachu to approach very quickly. However, it returns in Super Smash Bros. 4, except it can no longer be used on flat surfaces and is less useful overall.
By aiming the first half of the quick attack down and to a direction against the ground, Pikachu loses all lag from the move. This allows Pikachu to cancel the Quick Attack into any aerial move outside of down aerial (called QAC flash or Quick Attack flash). This is usually used to combo into neutral aerial or Thunder KOs (both vertical and horizontal). Due to the properties of the move, it is possible to "stun" the opponent using the first half of the Quick Attack and then hitting them with an aerial, or constantly hitting one's shield.
The technique is considered vital for competitive Pikachu players, due to massively helping with its approach and aerial game, as well as giving it a getaway option and a way to maneuver around the stage. It can also easily play mindgames with the opponent and allow extended followups to certain moves knocking the opponent across the stage, if one's reflexes allow it. Notably, it is an efficient way to combo straight into a neutral aerial, as the lock properties of Quick Attack can keep the opponent in position so that they cannot avoid the neutral aerial, which has a startup of 3 frames. The technique is overall a great addition to Pikachu's combo and edge games.
QAC is also part of many techniques: