F

As a child, f was happy and content with the other Letters, with n being his best friend. One day, f was having fun with his other friends r, i, e, n, d, and s until l and o came and pulled a prank on n by shooting o into his face, knocking him down on the ground. Angered by this, f took revenge for n by using the Letters a, r, and t to create the word "fart", which embarrassed l by making it look like he farted. F and N, along with all the other Letters, laughed at l and made fun of him. Plotting revenge, l and o put f together with r, i, c and k to make the word "frick". Disgusted, all the Letters bludgeoned f in numerous ways, making him cry gems. l and o decided to pull their last prank and have n betray F and force n to join their side with everyone against him. F ran away to his cave and watched upon the lives of every other Letter until he was an adult. Sometime before his attack, F became an adult. First appearing in the episode "D", he began to take revenge and attack the other Letters, leading to a mission to stop F from torturing the Letters. F managed to kill the Letters C, H, J, and X (also responsible for P's death as she was used as a decoy of him). He also managed to kidnap D, E, I, R, and S, and along with him and N, they made the word “FRIENDS”. At his final battle with N, he got killed by getting blasted through the chest by a laser made by N, making a hole in his chest and cave, killing him, rendering him to be dead. In Now I Know My ABCs, the remaining Letters sadden as they realize that F wasn't evil. He also appears to have lost his pupils. In the epilogue, after Z reverses time, L and O's plan to force N to their side failed, surprised that N instead chose to defend F this time. F and N both get beaten up by L and O once more, but do not care as they are happy to see each other. They run to their cave together and as they reach the mouth of the cave, they embrace each other and smile at the camera. It is very likely that F no longer has thirst for revenge because he remained best friends with N. So, it is very likely he will remain alive in the future.

Number Lore: F's first appearance is a brief cameo at the beginning of One, where he's hugging N at the top of his cave. In Three, he is dancing with N. When N sees L and O being attacked, F simply chortles when he remembers what they've done to him. When he refuses to help N stop the Letters, he and N have a tussle, causing the ampersand to break, and N to fall off of the cave, and into V and A to for VAN. N sadly drives away, and F is left sad and alone. Near the end of the episode, L tosses the Calculator Ship at the cave after the Numbers' defeat. Upon noticing the ship flying towards him, F looks in brief terror until the ship crashes into him and the cave, but manages to use his gem’s powers to cast a protective barrier around himself last minute. Shortly after F breaks out of his barrier, L flies into F's cave and offers an insincere apology to F. When L gets distracted by a reflection of himself in one of the calculator gem’s storage hubs, F takes advantage of the situation to get back at L and push him inside the storage hub, effectively trapping him. L tries to retaliate by firing a chronic laser from his period gem to contain F, but this backfires: the laser bounces off of the inside of his storage hub and freezes L instead, much to F’s delight. Shortly afterwards, F’s question mark gem hovers into the crack of an adjacent damaged storage hub, which seeps with sludge that appears similar to the one F oozed out in previous episodes. F looks inside the cracks, only to be interrupted by N, who caught up to him. However, F shrugs off N, calls off their friendship and walks into the hub. Upon passing through the cracked storage hub, F enters the ship and follows his levitating gem through a series of corridors until reaching the ship's control room, all while N tries to unsuccessfully get his attention. The question mark gem then enters into the launch button and repairs and repowers the ship, which is recolored completely black with a white halo, and levitates. N proceeds to restrain the ship with his gem, but then the ship flies to planet 0 with him, alongside L and g, leaving him with the semicolon gem, feeling guilty.

As seen throughout the series, he was trying to form the word "FRIENDS".