The Splatoon 1 special weapon that turns the player into a giant squid is Kraken.
Kraken is a special weapon in the original Splatoon that transforms the Inkling into a large, powerful squid-like form for a limited time. While transformed, the player can move across surfaces and attack opponents, making the weapon useful for breaking through defended areas or escaping a dangerous position.
Like other specials in Splatoon, Kraken must be charged by covering the battlefield with the player’s team ink. Its transformation is temporary, so using it at the right moment matters: activating it near an enemy objective can force opponents to retreat, while activating it too early may waste its short window of power.
The other choices are also original Splatoon specials, but they do different jobs. Echo Locator reveals enemy positions, Inkstrike targets a selected area with a large attack, and Bubbler provides a protective shield. Kraken is the one associated with the giant-squid transformation. Splatoon 3 later introduced a reworked related special called Kraken Royale.