That letter looks like circles and gumballs are circles
So we start in Season 1 where Gumball and Darwin have to return a CD to the store and learn a lesson on love, and then they have to babysit Anais and accidentally flood the house and almost die, and then Gumball wants to find a third friend, which ultimately culminates in the beginning of Season 2, where Anais successfully uses her excellent strategic thinking to steal the TV remote and watch her show at 8pm, which proves to be useful later on. However, during Season 3, Gumball, Darwin, and a teacher Mr. Small discover the Void, an endless abyss where the world's mistakes end up. However, on their way back, a mistake named Rob hitches a ride secretly, making it back to the real world but also severely damaging him. By Season 4, Anais has used her small size and agile movement to save the family from being killed by a gas fire. Season 6 than shows Banana Barbara, mother of Banana Joe, having the ability to paint the future with 100% accuracy, which leads to her kidnapping by Rob, but all she paints is static. That episode ends with the creepy line, "But there is no future."
Season 6 ends when School Superintendent Evil comes and attempts to rid the school of cartoons. However, he is revealed to be Rob in disguise, who reveals that getting rid of it was the only way to stop the world from-
He awoke in the school late at night, before the Void came and destroyed it all.