Simpson grew in California.
When Casey was in third grade, he scored high school levels for all subjects in school.
Simpson was 3 years old when he began his acting career, landing his first gig on Frank TV in a comedy skit called Santa. He has been in numerous commercials and has appeared on ABC's The Goldbergs. He is a native of Los Angeles, California. He has an older sister who has appeared in his YouTube videos. He was featured in a Demi Moore Lifetime television movie called Five.
Simpson played Ricky in the Nickelodeon TV show Nicky, Ricky, Dicky & Dawn. He describes his character as an "overachieving straight A student" who always fights with Dawn to be the leader because they both believe they are the most responsible one in the group. He originally auditioned for Nicky (Aidan Gallagher's character), but over the course of 8 auditions, he auditioned for Ricky.
In 2017, Casey's character Ricky Harper was nominated for a Kids' Choice Award for Favorite Male TV Star and the Kids' Choice Award for Favorite TV Actor.
In 2017, he starred in Escape from Mr. Lemoncello's Library. He played Kyle Keeley, a 12-year-old kid who is stuck in a library where the books come to life.
Simpson plays the piano, sings, and raps in his spare time. hosted, performed, and sang at many events such as Lyrics For Life LA & NYC, Rock into Summer Concert, and Kids Choice Sports Red Carpet.
He has an older sister named Sabrina.
He knows all the U.S. state capitals and the U.S. Presidents in chronological order. He can also memorized the alphabet backwards, the Periodic Table, the Gettysburg Address, and over 100 digits of Pi.
Casey is constantly creating his own videos and content through social media platforms, from which he has gained great recognition. Through his own creativity, he has amassed 400,000 subscribers on YouTube, 1.5 million followers on Instagram, and over 5.6 million fans on Musical.ly.