Cappy

Cappy is a mascot of the Nuka-Cola Corporation, used for promotion at the Nuka-World amusement park before the Great War.

Background
Cappy, a Nuka-Cola bottlecap, was used for marketing purposes and was featured in a park safety rules guide and on postcards along with their friend Bottle. They lived in Cappy's treehouse.

Nuka-World
Cappy is one half of Nuka-World mascots, Bottle & Cappy. He can also be seen in various Nuka-World advertisements, and in The Grand Tour sub quests icons. He is also the character used for the Hidden Cappy contest, in the glasses required to find the hidden Cappy clues.

Fallout Shelter
Cappy and Bottle are kidnapped by a raider gang in the quest series "Nabbed from Nuka-World". After freeing them, the pair will appear in the vault sporadically. They provide a temporary 20% happiness increase to every dweller, regardless of which room they are in. After they leave, dweller happiness is returned to their previous level. Tapping either one of the mascots when they stop and dance will yield caps, with Bottle occasionally yielding Nuka-Cola Quantum.

Appearances
Cappy appears in the Fallout 4 add-on Nuka-World and Fallout Shelter. Posters and statues of Cappy also appear in Fallout 76.