The Top Hat once required the Alchemy Engine to craft. That was changed in the Hungry for Your Hunger update due to the addition of the Prestihatitator, which requires one Top Hat in the recipe and is prototyped with the Science Machine.
The Dress Tab's icon is a teal version of the Top Hat.
If playing as Wendy, the Top Hat will almost completely negate the effects of night sanity drain in normal conditions due to her lesser fear of night.
Note that despite the sanity icon not displaying an arrow going down, the Top Hat will not completely negate said effects.