It's common knowledge on Alternia that clowns are the kind of people that you don't want to make mad for any reason at all. What the other trolls don't understand that it is very difficult to be a matesprit or kismesis with a clown. Most trolls don't even try to fill any quadrants with clowns, for reasons that I don't know myself.
To Gamzee though, it seemed like his friends didn't think that. They talked with him as if they didn't care if it was dangerous to be his friend. Even though, at times when no one was talking to him and he wasn't doing anything at all, Gamzee wondered if they will ever be scared of him. He pondered and pondered what would his friends do if he ever runs out of sopor slime. Of course, he thought that they would help him through it, like good friends.
After one of his fellow clowns went sober and killed nearly everyone he knew, Gamzee became quite afraid of what he would do if he ever went sober. One time, he nearly tried to make himself go sober to see what he would do, but couldn't let himself do that. He was too afraid of hurting his friends to let his stupid curiosity get the better of him.
When Gamzee learned that everyone is going to play the game, he got a lot of sopor slime to help him stay high. The fear of going sober on his friends and killing them haunts him every time he bakes a new pie. That sopor slime lasted in till that one fated day, that day on the meteor that we all know.
As Gamzee lies on the bottom of the cliff, the three long scratches that he made himself have are still bleeding. He is not in his murderous mode, thanks to Kanaya kicking him. He stares up into the darkness that is always in this meteor, remembering how he killed his friends. He goes over and over, their scared faces standing out the most in his mind.
This is where he gets the idea to help the new human players. Of course, it is going to be in his strange way, but he thinks it will be a great idea.
He gets up and begins his new plan. His new crazy, clown like plan.