Rat in the Hat

• WWizards of the Coast2022-10-07
  Official Ruling
  You "have a hat" if you have a hat with you, not if you own one somewhere. You don't have to be wearing the hat. But if you have a hat with you, why wouldn't you be wearing it? Does it not fit? Is it for a sports team that's bad? Did you just get your hair done? We're just curious. You don't have to explain.
• WWizards of the Coast2022-10-07
  Official Ruling
  A hat is a garment worn on the head that's not part of another garment. Hoodies, for example, are not hats. Items that cover only the face and not the top of the head, such as a face mask, are also not hats. Hats are purposely decorative. Simply balancing a thing on your head doesn't make that thing a hat.
• WWizards of the Coast2022-10-07
  Official Ruling
  Key in this set—space helmets are not hats, although some creatures with space helmets also are wearing hats underneath those helmets.
• WWizards of the Coast2022-10-07
  Official Ruling
  The above information pertaining to hats for creatures also pertains to actual hats for players.
• WWizards of the Coast2022-10-07
  Official Ruling
  A creature "has a hat" if the creature depicted in the art is in possession of a hat. That creature doesn't need to be wearing the hat. A background character such as a scale bird having a hat won't count.
• WWizards of the Coast2022-10-07
  Official Ruling
  No player can remove another player's hat. That's unsporting conduct.
• WWizards of the Coast2022-10-07
  Official Ruling
  Wigs and headbands count as hats. There are wig and headband stickers.
• WWizards of the Coast2022-10-07
  Official Ruling
  You're "wearing a hat" if you're wearing a hat.

Rulings via Scryfall