Personality Islands

Personality Islands are islands that exist in the mind and make up someone's personality. Personality Islands are created when a Core Memory is formed. Riley Anderson has five Personality Islands: After Joy tries to get rid of a core memory created by Sadness, they are both vacuumed out of headquarters through a tube that sends newly created memories down to Long Term Memory, accidentally bringing all of the core memories with them. Since the Core Memories are absent from Emotions' Headquarters, the Islands slowly start to breakdown, eventually being destroyed by falling into the Memory Dump, causing Riley to lose her personality.
 * 1) Family Island
 * 2) Honesty Island
 * 3) Hockey Island
 * 4) Friendship Island
 * 5) Goofball Island

After Joy and Sadness return to Headquarters, and a new Core Memory is made containing both Emotions at the same time, the Islands are recreated (The new Sad/Joy Core Memory creates a new Family Island). New Islands, such as Boy Band Island are also added later, as Riley's personality develops.

Trivia

 * It is unknown if there is a limit to how many Personality Islands someone can have. While Riley has five at the beginning of the film, several more are created at the end. This suggests that as someone grows up, more of their personality develops, allowing for the creation of more Personality Islands. This is evidenced by the renovations made to Emotions' Headquarters at the end of the film, such as the larger control board.