Gunpowder first appears giving Brom a ride into town and jumping over the Sleepy Hollow boys who are sitting half-asleep around a picnic table. He then stops in front of a man sleeping atop a beer barrel at whom he neighs This wakes up the man who leaps into the air with a startled scream, kicks the barrel out from under his feet and onto its side so that when he lands, it is on solid ground. Gunpowder then watches as Brom leaps onto the barrel and rolls it over to the table, serving the boys and himself some beer. As Brom does this, Gunpowder as well as a few of the neighborhood dogs lick their lips in unison as they want to taste the beer too. At this, Brom breaks open the top of the barrel with one mighty blow of his large fist and sets it down in front of Gunpowder and the dogs so they can drink. Gunpowder appears a few days later, once again giving Brom a ride into town where he and his master see the boys trying to assist Katrina with her groceries. As they glare angrily at the boys and scare them away, Katrina comes out but is unimpressed when they bow to her and offer her a ride home. A little later, when she accepts Ichabod's offer to walk her home they become jealous and Gunpowder runs through mud, splattering it on Ichabod. As Brom picks up Katrina and her groceries on to his back, Gunpowder takes off for her house. However, when they arrive Ichabod jumps in front of them causing a big cloud of dust which he walks out of with Katrina. After the dust disappears Brom is seen holding Katrina's groceries but his horse has mysteriously disappeared and doesn't appear throughout the rest of the film.
Although, The Headless Horseman's horse resembles Gunpowder, (it might very well be him), and the Headless Horseman might be Brom in disguise, but that remains unknown, and unlikely in the film.
Since in the novel, it is sometimes believed that The Headless Horseman is Brom Bones in disguise, some people believe think that the horse that the horseman used was Gunpowder
Gunpowder drinking beer with the dogs.
Giving Katrina a ride home.
Startling the man atop the beer barrel
Gunpowder and Brom frowning at The Sleepy Hollow Boys
Bowing to Katrina
In Ichabod's cloud of dust
Arriving at Katrina's house
Waiting for Brom to load Katrina's groceries onto his back