“You two ugly mugs came here for the same reason as us! You want the fabled Chuckola Reserve! Boo! Boo, I say! You really think you can beat me to the punch? Well, open up those ears, punks! I Popple, shadow thief, filcher of the world's riches, bet you that I get the Chuckola Reserve first! ROOKIE GO TO IT!”
—Popple, Mario & Luigi: Superstar Saga
Popple is one of the main characters in Mario & Luigi: Superstar Saga. Popple, or the "Shadow Thief" as he calls himself, desires to be a super thief who dreams of getting rich quick. The Mario Bros. first run into Popple and his accomplice, Rookie (who is really an amnesiac Bowser) in the Chateau de Chucklehuck where they are after the secret of the brewery's world famous drink, Chuckola Cola. Engaging the bros. in battle, Mario and Luigi manage to beat Popple and the blank-minded Bowser. The two show up again when Mario and Luigi solve the puzzles of Chucklehuck Woods, but they end up being blasted into the sky by the Chuckolator. He has a tendency of saying "see?" at the end of most sentences.
The bros. encounter Rookie and Popple again in the basement of Woohoo Hooniversity, where they are trying to steal the Beanstar. The two groups end up fighting again, and even when using their own bros. move, Popple and Rookie still lose. Suddenly, after the battle, the head of a Princess Peach robot falls through the ceiling and its voice irritates the Beanstar so much it bursts through the ceiling, taking Mario, Luigi, Rookie and Popple with it. The Beanstar then divides into four pieces flinging all its passengers off. Mario lands with Luigi in Oho Oasis, while Bowser is flung to Stardust Fields, where he is soon used as a revival power for Cackletta's spirit. Popple's landing destination is unknown.
Popple appears again in Chucklehuck Woods trying to get a piece of the Beanstar off a statue. The Mario Bros. fight him again, but this time without Bowser. After losing, he swears revenge upon the two and spins himself into the dirt below to escape. Popple appears again later, having made a base in Teehee Valley. After finding an unconscious Luigi in the desert, he takes him as a prisoner to lure Mario to his base. After Mario frees Luigi, Popple attacks and introduces his new Rookie, Birdo, who has fallen hopelessly in love with him. After losing in battle, Popple blames his defeat on Birdo, calls her useless and Birdo, heart-broken, knocks him through the wall. Popple is then sentenced to community service in Little Fungitown where he is last seen, and ironically, his supervisor calls him Rookie.
 Battle Strategy
In the first battle against the wannabe thief, Popple is accompanied by his loyal servant, Rookie. Whenever Popple is attacked, Rookie spams each brother with a hammer, which goes faster than normal. Because of that, many players decide to kill Rookie first, which makes Popple run away. However, defeating Popple causes the player to get 50 more experience points and 30 more coins. All Popple does is either do a simple ram into the opponent or steal their Mushroom and either heals himself or Rookie the next turn. This is can be determined by seeing if he grins or not; if he does it's to Luigi, if not it's to Mario. Determining his actual move depends on how the players defend themselves. If they can defend themselves by jumping, he is trying to ram one of the brothers, if they can defend themselves by using hammers, he is trying to steal a mushroom.
The second time the Mario Bros. fight him, he does the same moves until Rookie gets hurt about halfway. Then they start doing "Bros. Attacks" of their own, which always have Popple getting hurt. The first one has Rookie tossing Popple in the air, then he jumps and grabs Popple, then piledrives him into the ground to create shockwaves that the brothers both need to jump over. The second one has Rookie light Popple on fire, then he swings him towards a brother who has to counter with the hammer. The third time Popple is alone, he has two new attacks. One is where he grabs a money bag and starts throwing random detritus. Most of the time the junk are coins and a mushroom. Occasionally, however, he will throw out a Poison Mushroom and a monster similar to a Designbomb. These items will either come straight at the brothers or bounce towards them, so they will only get hit by them if they jump. The second new move is a little more dangerous. He turns around then he has either the grin on his face or his normal mad expression, then he tries to steal the brother's hammer. This can be countered with the hammer, but if not blocked correctly, Popple steals the hammer and uses it against them. Also, that brother can't attack with the hammer either except for Fire Bros. and Thunder Bros. when advanced. The hammer later returns to their possession after a few turns. Later he fights with Birdo by his side with all of the moves that he had by himself.
 Stat Information
 Names in Other Languages
||Pun on the word épargne (French for savings).
||Pun on klau (German for theft) and the German name Claude.
||Reference to how Popple is a champ while Rookie is a rookie.
- In Paper Mario: The Thousand-Year Door, a reference to Popple is made when Bowser visits Poshley Sanctum to steal the Garnet Star. When Pennington asks him who he is, one of the answers is "The Shadow Thief", which is what Popple calls himself. Also, if the player selects this title, Bowser will say "I'll be taking this, thanks!", a reference to Popple's "I'll be takin' this, see?"
- Popple's theme plays during the battle against Fawful at Bowser's Castle. Note that in Japanese version the music of Fawful's battle is the same that sounds in the battle against Cackletta in Woohoo Hooniversity.
- When Popple is encountered alone in Chucklehuck Woods, he has 520 HP. However, when he is next encountered (with Birdo at his side), his total HP is 500.
- Popple is similar to Croco, as they are both robbers in Mario RPGs, are both encountered at least three times by the player, and are fought multiple times in their respective games.
- In the last fight with him, when he steals the hammer, it shows he has a Super Hammer. The brothers have Ultra Hammers at this point.
- Popple is the only boss other than Jojora who is not required to be defeated (with the exception of his third fight), but can be defeated for extra experience, coins and items.
- Popple is briefly playable at the end of the barrel maze in Chateau de Chucklehuck. He replaces whichever bro is in the back. He runs off when seen, and the other Bro returns.