PK Thunder (PKサンダー, PK Thunder) is the up special move for Ness and Lucas. The move creates a stream of lightning consisting of two parts: a circular “head” which is controlled by the player using the control stick or d-pad, and a “tail” which follows behind. As control stick and d-pad inputs are used to aim PK Thunder, Ness and Lucas are unable to move or defend while the move is active. PK Thunder can be aimed into opponents to deal damage with the head and stun with the tail.
Aiming the head into Ness and Lucas themselves will launch them in a trajectory opposite to the side they were hit on. This is referred to as PK Thunder Tackle or PK Thunder 2. PK Thunder 2 is Ness and Lucas's main method of recovery and will damage any opponents that come into contact with them while in this state.
PK Thunder's head has a direction of knockback 90 degrees clockwise in relation to the direction it's moving. Each side can hit a shield safely without it disappearing, and due to hitbox renewal (the attack can only hit once every 48 frames) it is possible for the attack to safely go through shields. The tail cannot be cancelled.
Ness's version of PK Thunder has a more blueish coloring to it, and he hunches over when using it. The head of Ness's PK Thunder disappears upon contact with most attacks, walls, and characters. Impact deals 8% damage and knockback, and launches in the direction the opponent was hit, but can't launch downward.
In Melee, PK Thunder does not disappear on contact with most attacks, as it is a laser projectile similar to Fox's blaster. In version 1.00 of Melee, an uncontrolled PK Thunder can hit opponents and Ness himself. This means the player can intentionally hit Ness with the tail of PK Thunder to block him from flying off the screen. This technique is called a PK Thunder Barrier. PK Thunder can also be used to perform the Electric Ness glitch, where sparks will continue to show around Ness even when PK Thunder is not active. This glitch serves no offensive or defensive purpose.
In Brawl, PK Thunder turns in a tighter circle than previous games, meaning it can be used to recover in narrower spaces.
Lucas's version of PK Thunder has a more vibrant purple tint to it, and he strikes a different pose than Ness when using it. Additionally, the head of Lucas's PK Thunder goes through enemies and some objects, allowing it to score multiple hits. Each impact deals 9 to 10% of damage. Compared to Ness in Brawl, Lucas's PK Thunder also moves more slowly, has a shorter tail which deals less stun, and turns in a tighter circle — the latter meaning it is more favourable for recovery in narrow spaces. In SSB4, its ending lag is also much higher when used on the ground. Ness's second PK Thunder variant in SSB4 shares some similarities with this version.
PK Thunder 2
PK Thunder 2, or "PK Rocket", is the term used for hitting Ness or Lucas with their own PK Thunder while it is still under their control. The Japanese developers dubbed this move PK Jibaku (PK自爆). The word jibaku means 'self-destruct' or 'suicide bomb,' a fitting term for a tactic that turns Ness and Lucas into human missiles. This technique can be used by Ness and Lucas. Doing so will transform Ness or Lucas into a human projectile, which will move in different directions depending on what part of the body is hit. If the Ness or Lucas makes contact with an enemy, he will deal a good amount of damage and knockback. CPUs playing as either Ness or Lucas are also programmed to use this strategy, but they only use PK Thunder 2 vertically, even in situations where only recovering horizontally or diagonally would prevent death. PK Thunder 2 is also Ness and Lucas's main method of recovery, given that it launches them fairly far in a straight direction. While using the move, the user will fall much slower. When PK Thunder 2 is aimed downwards towards the ground, Ness or Lucas will enter a lying position, facing downwards. In Ultimate, an arrow denotes the direction Ness or Lucas will move in upon initiating PK Thunder 2; Special Zoom also occurs if PK Thunder 2 successfully connects against an opponent.
While it is a strong recovery move, it is also very linear and predictable. As the move causes helplessness if it ends in mid-air, it is extremely susceptible to gimps as the projectile produced by PK Thunder can be destroyed, absorbed, reflected, pocketed, or blocked by the stage.
In Smash 4 and Ultimate, if Ness or Lucas hit a wall during PK Thunder 2, they can use the move again in midair, but only during the moment between hitting the wall and entering their helpless animations. They can only do this once; hitting a wall again with the second PK Thunder without touching the ground or grabbing the ledge will result in immediate helplessness.
Ness's version of PK Thunder 2 deals one strong blow. If used up close in Brawl and Smash 4, it can bring Ness to a short stop. If Ness' PK Thunder 2 hits an opponent, it does 25% damage with extremely high knockback, KOing opponents at 75% in Melee, 50% in Brawl, and 30% in Smash 4. The distance of PK Thunder 2 can be shortened by angling it into the environment. If Ness hits a wall while flying, he'll bounce off of it as his flight direction is changed.
Ness' PK Thunder curves in a larger arc than Lucas, so Lucas requires less room to use PK Thunder 2 than Ness. However, Ness' PK Thunder is faster.
Lucas's version of the attack hits multiple times, compared to Ness's one strong blow. It is interesting to note that Lucas's PK Thunder 2 covers more ground than Ness's, so Lucas's is slightly more effective when recovering. If all of Lucas's hits connect when using PK Thunder 2, it will deal a massive 43% damage in Brawl, 35.5% in Smash 4 and 32.5% in Ultimate with high knockback, making it Lucas' most damage-dealing move, with the exception of PK Starstorm, which cannot be used in competitive play. However, it is very hard to get full damage, as PK Thunder 2 takes very long to start and as such, is easily dodgeable. For tactical uses, Lucas's PK Thunder 2 can be used to "Thunderglide". Thundergliding is when the player runs off a platform then immediately uses PK Thunder. The effect should come out to being the PK Thunder being much closer to Lucas than normal. Then, guide the thunder into Lucas and he should angle down towards the ground. If performed right, Lucas's direction will go from diagonal to horizontal as he glides along the ground. Otherwise, he'll crash into the ground like a normal poorly aimed thunder. Lucas will stop at the edge on his own, making this move safe to use on a stage like Battlefield. It should also be noted that on stages like Battlefield or Final Destination if Lucas's PK Thunder 2 is aimed wrong, the user will bounce right off the corner of the stage, leaving him in a helpless animation away from the ledge.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Like the other DLC characters, Lucas has no custom move variations.
PK Thunder (localized as PSI Thunder in EarthBound) has appeared in all three Mother games, where psychic power is used to send lightning at the enemy. However, in the Mother series, neither Ness nor Lucas learn the move; instead it is learned by some of their friends and party members, Paula and Poo in EarthBound and Kumatora in Mother 3 respectively.
The move's description in EarthBound states that the user could miss the target and not cause any damage to the enemy. The difficulty of using PK Thunder in the Super Smash Bros. games could be a reference to how PK Thunder can sometimes miss enemies in EarthBound. The move's recovery properties are somewhat similar to Teleport α, where the party's speed is increased greatly, to the point of being difficult to control, and explode if they hit a solid object before covering sufficient ground to warp.