"The Ren & Stimpy Show" creator John Kricfalusi is back in the world of "The Simpsons" as the guest animator of this year's "Treehouse of Horror" couch gag, a two-minute clip rendered in his unmistakable style and featuring Bart, Lisa and Maggie chased by the ghost of Frank Grimes. It sets the stage for the latest installment of what's become a 25-year tradition -- annual Halloween specials that delve into different genres and tones, far outside the show's already loose continuity.

"[The 'Treehouse of Horror' episodes] are pretty much my favorite ones, because they do weird stuff in them," Kricfalusi told press including SPINOFF ONLINE during a conference call. "They break all the rules, which I love. I don't like rules myself."

Kricfalusi first brought his gleefully gross vision to "The Simpsons" in 2011 with the opening sequence to "Bart Stops to Smell the Roosevelts." This year's "Treehouse of Horror" opening -- "Treehouse of Horror XXVI" if you're counting -- features Kricfalusi also paying tribute to Hanna-Barbera character Huckleberry Hound, in the form of the deliberately off-model Halloween costumes worn by Bart and Lisa.

"We didn't think we could get the rights to them," Kricfalusi said. "At the last minute, I called [Warner Bros. Animation President] Sam Register over at Warner Bros.; they own the Hanna Barbera characters, and they gave us permission. That was cool."

"It was a real Huckleberry Hound mask," longtime "Simpsons" showrunner Al Jean added.

"And it was the wrong color, too," Kricfalusi said. "Just like the Huckleberry Hound merchandise when I was a kid."

Though Kricfalusi has more than 35 years of experience in animation, it appears his work is still evolving -- and he told reporters that the "Treehouse of Horror" opening was something of an experiment for him in a new approach in emphasizing character movement as part of the humor.

"We tried a new style of animation on this," Kricfalusi said. "Not only do the holds -- the main poses -- look funny, like on 'Ren and Stimpy,' but I've been trying a new type of animation where even the in-betweens are weird, and the way it moves is funny."

Jean, who said his main contribution to the opening was suggesting the inclusion of Frank Grimes -- from the beloved/infamous season eight episode "Homer's Enemy" -- admitted that he was once skeptical on how long the show could maintain its annual streak of Halloween specials.

"I thought the plotting on the 'To Serve Man' [segment, 'Hungry are the Damned'] was unbelievable on the first 'Treehouse,'" Jean said during the call. "But I actually was the one who said after the third one, 'I don't know how many more of these we have left.' Of course, it's probably the most popular single episode we do every year. Everybody looks forward to it, not just fans, but on our side, just because everything's a different style -- every director who works on it really steps up."

"Treehouse of Horror XXVI" -- including a Godzilla parody and a story where Sideshow Bob finally succeeds in killing Bart -- airs 8 tonight on Fox.