From the Super Mario Wiki
Snawfuls are snowman-like enemies that assist Blizzard Midbus during the events of Mario & Luigi: Bowser's Inside Story. In battle, these enemies attempt to freeze Mario, Luigi, or Bowser. When defeated outside of Bowser, they simply melt, but when inside, they melt and leave cold air inside Bowser, usable for later. After taking out a Snawful inside Bowser's body, a counter of how many Snawfuls have been defeated is shown. If the Mario Brothers can defeat five Snawfuls, Bowser breathes out enough cold air to make it set an ice ball on top of Midbus's crown, disabling him from making any more Snawfuls, thereby making the battle easier. If Bowser uses attacks such as Flame, Magikoopa Mob or Koopa Corps, the Snawfuls hide in their hats.
As they are made of snow, Snawfuls are weak against fire.
Names in other languages
|Snowbits, from English "snow" and Fawful's Japanese name, Gerakobits.
||Snawful, from Spanish "snow" and Fawful.
||Muñécovitz is a pun on Muñeco (Doll, but note that Snowman is Muñeco de Nieve in Spanish) and Grácovitz (Fawful's European Spanish name). Gélido means Gelid.
||Pun on Gracowitz (Fawful's European French name) and neige (snow).
||Pupazzo di Ghigno
||Pun on Pupazzo di neve (snowman) and Sogghigno (Fawful)