Oh, Hi, Shy Guy!
From the Super Mario Wiki
Oh, Hi, Shy Guy! is the first secret level of the Beanbean Kingdom in the Minion Quest: The Search for Bowser mode in Mario & Luigi: Superstar Saga + Bowser's Minions. In order to obtain this level, the player has to use certain amiibo to unlock it.
The level consists of mostly Shy Guys and Fly Guys and has two battles. The first battle has two Fly Guys in the front, five Shy Guys in the back, and a Shy Guy captain. The second battle has five Fly Guys at the front, two Shy Guys in the back, and a Fly Guy captain.