Popple's Partner, Part 2
From the Super Mario Wiki
Popple's Partner, Part 2 is the second bonus level of Teehee Valley in the Minion Quest: The Search for Bowser mode in Mario & Luigi: Superstar Saga + Bowser's Minions. This level is available after completing Toad Rescue and after Cackletta becomes Bowletta in the main game.
The assisting Lakitu informs the Goomba Squad that Popple had been spotted in the valley. Believing Bowser to still be there, the minions give chase, only to find that Bowser was not there, but Popple wanted to one-up them anyways, and a battle ensues. The Goomba Squad battles Parabeanies, Beanerang Bros, Elite Troopeas, and Birdo and Popple themselves. After Popple is defeated, Captain Goomba begins to wonder where Bowser is. A brief cutscene plays, similar to the main game, showing Fawful transferring Cackletta's spirit to Bowser's body, turning into Bowletta.