Koopa Troopa Trouble
From the Super Mario Wiki, the Mario encyclopedia
Koopa Troopa Trouble is a level in Bowser's Castle (East) in the Bowser Jr.'s Journey mode of Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey.
After Bowser Jr. passes Captain Boo, Captain Koopa Troopa halts him to the next battle, only to tell him that he gave up doing rhymes and that he nowadays tells jokes. After the battle, Ludwig tries to tell Bowser Jr. on what he has went over through learning how to battle. Bowser Jr. tells Ludwig that he is better off without his help. Ludwig tries to teach Bowser Jr. once more, but Bowser Jr. ignores him by saying "Duh!" repeatedly at him, making it frustrating for him to teach him anything.