When the player uses PK Freeze, Lucas fires a PSI-based snowflake into the air, charging up its power while the crystal hovers in the air. After the snowflake charges enough, it will explode, freezing anyone in the surrounding area, as well as harshly damaging the players who are hit. If the crystal hits any terrain while it is charging, it will disappear harmlessly, causing endlag that can be punished, so the player must release the button at the right time. Lucas does not have to wait for the snowflake to charge completely, however, and can unleash its icy energy when the time seems right. Lucas will stop the attack if he gets hit, much like Ness will stop when attacked during his PK Flash. Compared to PK Flash, PK Freeze has far more horizontal mobility and charges much faster. PK Freeze does gain slight power and the opponent stays frozen longer if PK Freeze is at its largest. At its smallest, the opponent is frozen for a shorter period of time. To compensate for its ability to freeze, it has a lower damage output and less knockback than PK Flash.
In Brawl, a fully-charged PK Freeze will explode before reaching past where Lucas is standing, making it effective on flat terrain. However, in Smash 4, the move will continue to drop past Lucas's level if left to fully charge, hitting the floor and nullifying the attack, not unlike all iterations of Ness's PK Flash. Therefore, the player must keep in mind to release the button and fire off the move before it hits the floor. Initiating the move after a short hop will also ensure one gets the most out of the attack.
In Ultimate, PK Freeze no longer dissipates when it touches any terrain and also can move through soft platforms. The knockback it deals is now diagonal as opposed to upward, making it kill unusually early. Using it in the air no longer leaves Lucas helpless.
In Super Smash Bros. 4, Ness can customize his standard neutral special, PK Flash, into PK Freeze. The move behaves similarly to PK Flash (and not Lucas's PK Freeze), with lower damage output and knockback. In return, the move freezes opponents. Ness's version does not take on the snowflake appearance of Lucas' version and instead looks like a PK Flash with a deeper blue color compared to the original PK Flash itself. Unlike the PK Freeze of Lucas, it can never KO normally, but if the opponent is at a high enough percentage, Ness can use an attack to knock them offstage.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Like the other DLC characters, Lucas lacks custom move variations.
PK Freeze (localized as PSI Freeze in EarthBound) first appeared in Mother and has appeared in later Mother games since. In all of three of the Mother games, the move involved using the character's psychic power to cause ice damage to enemies. However, in the Mother series, Lucas and Ness cannot 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.
In the description for the move in EarthBound, it states that the player causes a very cold swirl to go around an enemy and could cause the enemy to freeze, but when in battle, it shows hexagons and squares circling on the enemy. The same is true for Mother 3. Also, when Lucas performs the move, in Super Smash Bros. Brawl, a snowflake inside a hexagon can be seen before "exploding", which may be reference to the octagons that appear when PK Freeze is used in battle.