From the Super Mario Wiki
Paratroopa is a character in Mario Party Advance. He runs the only item shop in Shroom City, Junk, and he is Koopa's cousin. According to his description, he acts as a "big-brother type" and looks after the townsfolk. Paratroopa is one of the few characters to not give a quest, but he and his shop are involved in several other quests. If the store is entered while a relevant quest has not been taken, Paratroopa says that the shop is closed, but also that it is going to open soon.
During Bob-omb's quest, Find the Password, Bob-omb tells the player to go to Junk and buy a Bob-omb figure. If Paratroopa is asked about the Bob-omb figure, he reveals that he is a part of the Bob-omb group as well. He provides the password to enter the group, "Baboom." A Toad Force V figure can also be asked about, but Paratroopa says that there are no more of those figures due to the show's popularity and that the shop is receiving more of them soon.
In another quest, Probably a Robbery?, Paratroopa is one of the three suspects in the robbery of the Koopa Bank, run by Koopa. The bank went pitch-black and a bunch of coins were then stolen. When questioned about what happened, Paratroopa claims that he was so surprised during the entire incident he dropped to the floor, but that he saw the shine of the stolen coins. He can also be questioned about the state of the shop, to which he claims that everything is going great. After all of the suspects are interrogated, Paratroopa is identified as the culprit. Koopa insists that Paratroopa would not steal from him since they are cousins. Shroomlock explains that Paratroopa lied while being interrogated, since he claimed to have seen the coins even though the darkness would have prevented him from seeing anything. Paratroopa soon flies in to explain that he only wanted to play a prank on Koopa, and he is forgiven and allowed to walk away instead of being taken to jail. He is incredibly thankful and flies off to return the coins.
During Bowser's quest at the Bowser Pad, Accessorize!, Bowser asks the player to go to Junk and buy him "the perfect gift," which the player has to choose from a ring, necklace, or bracelet. At the item shop, Paratroopa says that he was informed by Bowser of the player's arrival, and gives him the option of the three accessories. Regardless of what is selected, Paratroopa always says that Bowser is going to love the gift.