Jr. Troopa

Jr. Troopa is the tertiary antagonist of Paper Mario. He constantly tries to ambush Mario and his friends during their quest to prove himself to be stronger than Mario.

Paper Mario
Jr. Troopa is a young koopa who uses his eggshell to protect himself from any attack. He has his own place territory called "Jr. Troopa's Playground". He always likes to bully any kid in his sight. After Mario went to his territory to get the Goomba's Hammer, Jr. Troopa notices him and challenges Mario to a battle in which Mario wins thanks to the new ability of the Hammer.

Paper Mario: The Thousand-Year Door
Jr. Troopa makes a cameo in the background of Zip Toad's photo with the same form he used to battle Mario in Toad Town. This could mean that Jr. Troopa is still obsessed with find Mario and defeat him.