Joker Balloons

Joker Balloons are part of a small challenge to pop a small, tied down group of balloons with devious smiles on them.

They are similar to the TYGER Security Cameras, mounted objects that you must destroy for The Riddler's Challenges.

Batgirl: A Matter of Family Incident
Multiple patches of Balloons were strung around Seagate Amusement Park. Destroying them all, along with Joker Teeth and Harley Quinn's Jack-In-A-Boxes are required for a achievement/trophy.

Arkham City Incident
Small groups of Joker Balloons are scattered around Arkham City. They are part of Riddler's Challenges and encompass bits of the Industrial District and Amusement Mile.

Trivia

 * The balloons can be popped with the Batarang, REC, Freeze Blast, or just by passing over them while gliding.
 * Balloons also appear in Arkham Knight, but are purely decoration. They can be popped just like Joker's Balloons.