Oh god, the headcanon that spawned this is so unbelievably sappy for me it hurts. More GamKar.
Basically Gamzee's dying, Karkat panics and spots a free Kernel sprite hovering around (don't ask where it came from I don't know) He throws cation to the winds completely and throws Gamzee at it. The result is God-Tier GamSprite because Gamzee was actually still partially alive.
But now Gamzee just sort of floats around Karkat, gving him hugs whenever he's depressed or gets excessively angry - imagine a comfort blanket that hovers around you everywhere and drives you nuts because he won't stop rambling and there's nothing you can do to shut him up, but you can't help loving the fact that it's there.