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Grumply-grumply-groo, we're here to share Christmas with you!
―The Grumple, wishing to spread holiday cheer, from his family, to the Simpsons and Gil[src]

The Grumple (also known as Grumpy Groo) is a green, hairy character (a parody of Dr. Seuss' the Grinch), which appears in Kill Gil: Vols. 1 & 2. He played a character that threatened to steal all of the Holiday cheer of the Winter Holidays in the Krusty’s Kristmas On Ice show. When a fight broke out between the basketball team and the show skaters (because the preparations for the upcoming game were ruining the show) Homer took matters to his own hands and fought the Grumple, demanding that he return the Holiday cheer. On Christmas Day, when Gil had all of his stuff stacked in the living room of the Simpsons House, Homer commented that this was a problem. Marge then commented that Homer had a bigger problem outside and pointed at the window. The Grumple was standing outside the house, holding a knife and proclaiming "Grumpily Grumpily Groo! Your blood will make my stew!" Homer suspects it was the same Grumple from the Ice Show. Sometime later in the year, while Gil was still mooching off the Simpsons, Homer was at Moe's Tavern and the Grumple attempted to attack again with a broken pool stick. Homer hit him with a beer bottle, knocking him unconscious, suddenly, some sort of green liquid began oozing out of the Grumple's eye, suggesting that it was not a human in a costume, but some sort of strange creature. The Grumple does not return until the following Christmas when the Simpson Family spend it at their condo in Scottsdale, Arizona with Gil, having brought his wife, son and daughter with him. The Grumple proclaims "Grumpily-grumpily-groo, we're here to share Christmas with you!" having put his feud with Homer aside as the humans and Grumples began singing Christmas Carols.

What the hell is this thing?!

He makes a second appearance in "The Falcon and the D'ohman” as a skater in the Christmas on Ice show.

When Lady Gaga comes to Springfield, he appears in the crowd of people cheering for Gaga.

He is also present in the "Harlem Shake" couch gag opening.

He is also mentioned by Matt Selman in the April 15, 2014 TV Guide article on "Brick Like Me" who jokes that he will be one of the few Simpsons characters to not be portrayed in Lego form during the episode.