Popple is a minor villain from Mario & Luigi: Superstar Saga, its remake, and Mario & Luigi: Dream Team. He's a thief who attempts to steal several treasures, putting him at conflict with Mario and Luigi.
Popple first appears in Chateau de Chucklehuck, alongside his partner "Rookie" who is actually Bowser. He and Rookie attempt to steal the secret of Chuckola Cola. They are defeated by the Mario brothers, and they are blasted into the sky by the Chuckolator.
Mario and Luigi later encounter Popple and Rookie in Woohoo University, where they try to steal the Beanstar. After they battle with each other, the Beanstar bursts into the sky, splits in four, and Popple, Rookie, Mario, and Luigi are all tossed off.
Popple appears once more in the Chucklehuck Woods, this time without Rookie, where he tries to get a part of the Beanstar from a statue. He is defeated once more.
Popple appears one more time in the game. He and his new Rookie, Birdo (who has fallen in love with him), imprison Luigi. However, he and Birdo still lose nonetheless. After the battle, Birdo knocks Popple through a wall. Popple is later sentenced to community service in Little Fungitown.
Popple serves the same role in the games remake as he did the original, but he also serves a role in the Bowser's Minions story. In the story, he finds an amnesiac Bowser in Hoohoo Village, and makes him his partner. He later gets in a scuffle with Captain Goomba and his fellow minions, which he loses. Bowser does not recognize his army however, and scares them away.
Popple appears later, after Bowser regained his memory. He tries to find a new Rookie, considering a Fighter Fly, a Beanie, a Paratroopea, and a Tanoomba. He gets into another scuffle with Captain Goomba and his minion squad, which he once again loses. With no other options, he lets Birdo become his new Rookie.
Popple makes an appearance in Mario & Luigi: Dream Team. He first appears after a failed robbery, and he doesn't recognize the Bros at first. Later in the game, in Wakeport, he mistakenly believes that a Wiggler (who wants to build a garden) is a security guard, and he insults the Wiggler enough to get him to attack the Mario Bros. After the battle, he fights the Bros himself, but loses. He then realizes that Wiggler is not a security guard after all, and insults him, causing the Wiggler to angrily chase him.