Aww, I feel a bit bad for the Great Pumpkin this year. Don't worry dude, you're still a hell of a lot prettier than your over-baked hay-wigged counterpart.
We try to avoid any sort of continuity or callbacks in our comics, but the Great Pumpkin is one of the few exceptions to this rule. The first time he emerged from his inter-dimensional rift was a few years ago in "The Gourdening". We had so much fun with the idea of a demonic pumpkin that we brought him back in "It Must Flow". For this year we originally had planned to do an over the top, action-oriented comic, but at the last minute decided to touch, once more (and hopefully for the last time) on the US election. It's kind of hard not to, given the circumstances.
Coincidentally, the other exception to our rule against continuity is the little kid in the Kirby costume, who is also one of our oldest recurring characters. He popped up extremely early, in one of the first comics we made, when Sarah was just starting to incorporate color into her cartooning, and since then he's popped up several times, notably around the holidays.