U

U is a lime Letter U. His eyes are on the top of his body (later moved down a bit since Number Lore) and his mouth is located at the bottom in the middle. He can walk around like a slinky. U is a helpful Letter who often gets left out and is also curious and confused. As a child, U was kind to the Letters. One day, f, l and o got into a fight, and when l pushed f to make him spell the word "frick", u and all the Letters got angry with f and beat him up.

In U, he is surprised by G and N confronting him, while the screen shows the word "GUN".

In V, G uses "GUN" right before F attacks V, which was unknowingly P. Realizing, U is shown to be devastated. The Letters mourn P.

In Y, all the Letters except V, running away from fear, enter F's cave cautiously. N picks up the gems, as all the Letters, including U, are swallowed by F's manipulation goo. When N shoots a rainbow ray at F, killing him, it frees all the Letters, before realizing F trying to spell "FRIENDS". Q then shows why F had did what he had did.

In Now I Know My ABCs, the Letters realize that F wasn't evil, and then Z reverts time. U first appeared in Number Lore in 3. He was seen dancing with the other vowels but their dancing was cut off shortly when the Calculator Ship flew over them. B tells the vowels that X got kidnapped which angered them. O transforms to his super form, E forms the BIKE and A flew with V. U, left alone walked liked a slinky but is slow and falls behind.

He appeared again in 4. As he was still inching his way to the other Letters, the Math-Machine and the Numbers ran through him making him go after them instead. He appeared again, looking at 4 when her attempt to restrain the ship failed, which allowed the Calculator Ship to escape.

In 5, he appeared again, where he was looking at the sky which is covered in falling debris and almost got hit by a boulder of rock from Z's ellipses. BIKE then picks up several letters, including U. T then made a hole in the ground to allow BIKE and the other letters to hide underground, he then covers it afterwards. T then revealed an underground systems of paths and caves.