Paper Boomerang Bro
From the Super Mario Wiki
Paper Boomerang Bros. are paper forms of Boomerang Bros. that appear as enemies in Mario & Luigi: Paper Jam. Paper Boomerang Bros. attack by throwing their boomerang at one of the bros. When the boomerang leaves the screen, the Paper Boomerang Bro jumps in front of another bro, indicating where the boomerang enters the screen from. They can also attack by throwing their boomerang, causing it to circle around one of the bros., and then folding themselves into a boomerang and circling the bro. This attack must be countered with a hammer in order to avoid damage. Occasionally, Paper Boomerang Bros. carry another Paper Boomerang Bro as a boomerang. Taking damage from these Paper Boomerang Bros. results in an additional Paper Boomerang Bro getting added to the battlefield. A maximum of nine Paper Boomerang Bros. can appear in battle, though this is only possible if two of them carry Paper Boomerang Bros. Paper Boomerang Bros. are found in Bowser's Castle and an area in Neo Bowser Castle.
Rare, shiny variants can also appear in place of the regular Paper Boomerang Bros. in the same areas. These Paper Boomerang Bros. have greater stats and always drop either an Ultrasyrup Jar or Shocking Boots when defeated, though their methods of attack remain the same.