Teleportation Circle

At the beginning of your end step, exile up to one target artifact or creature you control, then return that card to the battlefield under its owner's control.

Hat Trick

Target blocking or blocked creature you control gets +1/+1 and gains first strike until end of turn. If it has a hat, it gains double strike until end of turn. If you and that creature each have a hat, the creature gains triple strike until end of turn.

"Brims" Barone, Midway Mobster

When "Brims" Barone, Midway Mobster enters, put a +1/+1 counter on each other creature you control that has a hat.
"Brims" Barone, Midway Mobster has menace as long as you're wearing a hat.

Park Re-Entry

Return up to two target creature cards that each have a hat and/or mana value 3 or less from your graveyard to the battlefield.

Rat in the Hat

{T}, Sacrifice this creature: Until end of turn, you may cast target creature card that has a hat from your graveyard.

Haberthrasher

Deathtouch
Whenever another creature you control that has a hat enters or a hat sticker is put on a creature you control, each opponent loses 1 life.