Cheese Sandwich is a male Earth pony and the self-titled "super duper party pony" who appears in the episodes "Pinkie Pride," "Equestria Games," and "Twilight's Kingdom - Part 2." He later appeared in Season 9, and at the series finale where it's shown that he has been married to Pinkie Pie and has a foal of their own.
He was voiced by "Weird Al" Yankovic who also voices Milo Murphy.
Cheese Sandwich makes his debut as the featured guest character in Pinkie Pride. He is first shown on the outskirts of Applelooss, having just thrown a party for the ponies and buffalo. As he leaves, his Cheesy Sense points him in the direction of Ponyville.
When Cheese appears before Pinkie Pie and her friends, he introduces himself as the premiere party planner in all of Equestria. As his introductory song begins, he takes on a more excitable off-the-wall persona, playing the accordion and singing that he had wanted to be a party planner since he was a colt. At this point, he takes the reins of Pinkie Pie's party plans for Rainbow Dash and puts together a large birthday bash.
Later, when Pinkie feels her position as premiere party pony is threatened and challenges Cheese Sandwich to a goof off, Cheese accepts. During The Goof off, Cheese displays an even greater inclination for bizarre behavior, singing a polka version of Pinkie's Smile Song and having his own, much larger party cannon. Pinkie Pie, realizing that Rainbow Dash isn't having fun, concedes the goof off to Cheese.
Cheese Sandwich later approaches Pinkie and tells her he never meant to take her place in Ponyville. He confesses that he was actually extremely shy as a colt, and he didn't realize his dream until he left his Manehattan home and stumbled into Ponyville during a party thrown by the filly Pinkie Pie, which led to him earning his cutie mark. Having reached an understanding, Cheese Sandwich and Pinkie Pie team up to make Rainbow Dash's birthday party memorable.
Before he leaves Ponyville, Cheese gives his rubber chicken, Boneless, which he originally acquired in Ponyville at Pinkie's party, to Pinkie Pie and sets out with a second rubber chicken, Boneless Two.
During Equestria Games, Cheese is barely seen in the audience as Spike attempts to light the torch.
When initially introduced, Cheese Sandwich has a rather serious demeanor, dressing in a cowboy hat and poncho. At first, his comedic side is only hinted by a rubber chicken wearing a bowler hat, which he carries on a saddle and calls Boneless. He speaks in a rather serious tone reminiscent of Clint Eastwood and other spaghetti western heroes.
Later, he reveals his true excitable personality. He also shares many traits with Pinkie Pie: he enjoys acting out and turning a party into a grand performance. He loves to sing and can play the accordion, and he possesses a "Cheesy Sense" that, similar to Pinkie's Pinkie Sense, lets him know when parties are in the middle of being planned.
Toward the end of his debut episode, Cheese Sandwich is shown to hold Pinkie Pie in high regard, wanting to impress her with his skills as a party planner because of the impact she had on his life.
His cutie mark mirrors his love for cheese and accordions, which he frequently uses for his parties.