Tiny Rick is a younger version of Rick created through Operation Phoenix in the episode Big Trouble In Little Sanchez. By transferring his brain into a younger clone of himself, Rick is able to attend Harry Herpson High School. along with Morty and Summer in an effort to help catch a vampire within their school.
Tiny Rick has a very similar personality to older Rick. His down-to-earth style impresses the other students of the high school and he becomes very popular. However, over time his youthful personality begins to overpower his older consciousness in an attempt to stay young forever. His older consciousness fights against his younger mind by singing original songs with lyrics that are used as a cry for help, such as Let Me Out.
Tiny Rick attempts to destroy his older body but is stopped by Morty and Summer. Using an Elliott Smith song, Summer is able to get through to the older Rick, and he walks them through transferring his mind back to his original body.