J

J did not show up as a lowercase Letter until after f pulled a fart prank on l, and l retaliated by making f spell "frick". When most of the letters glare at f and hurt him. j then shot f using his cannonball-shooting ability, damaging f's teeth and showing why F's teeth are so sharp. After breaking F's teeth, he watches i, m, x, t, e and d attack f. After the fight, he watches n betray f which causes f to run towards his cave. After l, m, n, o, p, and x got their gems, j and the other letters turn their backs on f. Except for q, who tries to warn them that something bad will happen once their uppercase letters.

Somewhere before F's attack, J turned into an uppercase letter.

Right after debuting in J, he got executed by F from a cannonball from I, turning him into ashes. The only letter that cared for him was K. His ashes stood there from K, L, M, N, O, P, and Q's episodes. In R, After the CAB leaves, Q slugs on his ashes without even noticing. In the epilogue, Z rewinds time to recover all the letters that were attacked by F which includes F himself. J appears again as a lowercase letter again and watches N stand up for F. After N stands up for F, J moves to a spot near the edge of Z with W.

Before the Number's attack, J turned into an uppercase letter. In the new timeline, J is alive and well; as a result, he plays a much bigger role in this season. He alongside W was residing by the cliff on Z when the Calculator Ship showed up and crashed into the ground, nearly reaching him, but stopped just before. J also watched Clone 1 and 2 make 3. After 3 was made, he blasts a fire beam at J, but he was quickly saved by K and she used him to fire his laser beam back at 3, causing a war to go on. While J was succeeding, 3 swoops his tongue through and forcefully grabs him and K, slamming them into the ground and mildly injuring both Letters. J appears again when L uses his gem to pick up the Calculator Ship and hurls it into F's cave.

In the succeeding episode, shortly after L hurled the calculator ship into F's cave, J was among the Letters who looked at L in disgust as the latter laughed at F's presumed demise, alongside E, R, and K. They indirectly called L a jerk by lining up to spell the word, which therefore revealed his true nature. Both he and K also appear to be completely unscathed, implying they quickly recovered from their struggle against 3. As L leaves to follow VAN, J then witnesses VAN transform into VAÑ. He then sees it speed towards F's cave. Behind J and the other Letters, 1 (still entrapped with his clone, 2, and 3) uses a blowtorch on O's colon gem to free him and his allies. 1 then successfully burns the colon gem off and frees himself and the Numbers, J and the other Letters turn around and look shocked as 1 and 2 tower above them. 1 is on top of 2's head, with 3 and 1's clone in the equation machine. 3 lashes his tongue around 2's jaw, which 2 bites down on like a rein. 1 mounts his device on top of his head to evoke the appearance of a cowboy hat. 2 then takes off like a horse and knocks J and the other letters over like bowling pins.

In 5, BIKE, N, and O pick J up, as well as several other Letters. The 5 clones chase the Letters as they try to pick up H but are unable because H is a ghost and sped off while the clones of 5 trample them. T reintroduces himself, but the Letters almost run over him again, and he looks at the chaos before joining the chase. T makes a hole for the Letters to go into as BIKE speeds up. A clone of 5 almost bites J's chin, but he is saved by C. The Letters fall underground as T seals up the hole as the clones stampeded through. Later in the episode, J appears again when T leads the group to his bunker, where he shouts for any intruders present in his bunker. Not much is known about J, other than the fact he was angry at f for spelling "frick" when younger and blasted his teeth with a cannonball. He likely keeps to himself but helps when provoked or needed, such as battling 3 after almost being killed by him. It's also likely J regretted shooting F's teeth in 4 as he called L out by spelling "JERK".