Balloons

The Balloons make their appearance in "Ricardio the Heart Guy". They fly up on screen in the episode when Princess Bubblegum says that she'll throw a party for Finn and Jake for rescuing her from Ice King once again. The screen says PARTY TIME! and the balloons fly up.

They appear in "What is Life?", and they have more importance in the episode. In "What is Life?", it is mentioned that they are great pranksters. One of them said that he stole Finn's wallet; this seems impossible because the balloons have no arms. The balloons seem to be indebted to Finn. When they fulfill their obligation to Finn, he allows them to float into the Mesosphere and die.

They also make a cameo in the beginning of The Duke when Finn and Jake throws bottles of magic at a wall.

Finn says they are Grade-A pranksters.

Appearance
The balloons are all similar-looking with a variation of colors. However, one of the balloons seems to have a horribly disfigured face, it is currently unknown as of why this is. Seeing as the Land of Ooo is a strange place, it may be normal for the other residents there.

In "What Is Life?," Finn holds them to take him to Ice King's lair. Finn bumps into a mountain and when he asks if they meant to bump him,and they said, "Yeah."