The Clown That Honked 1000 Ships Achievement in Costume Quest 2
The Clown That Honked 1000 Ships50
Used the clown horn 1000 times
How to unlock The Clown That Honked 1000 Ships
The Clown Costume is one of the first costumes you'll get. It's story related so you can't miss it. Once you have it, equip it and press to honk the horn.
The clown horn is used in a few early quests and also used to scare away crocodiles and pigeons. You'll have used it quite a few times by the time you're done with those. After that, find some spare time whenever and just mash on until it unlocks. It shouldn't take more than 5 minutes or so.