Frankie was "discovered" at a talent show in Raleigh, North Carolina, where he was featured as Tiny Tim in a production A Christmas Carol. After this, his parents divorced and he and his mother moved to Burbank, CA. He then landed a role in the 1997 television film To Dance With Olivia along-side Louis Gosset, Jr. A few minor productions later, Frankie landed the role of Malcolm in Malcolm in the Middle.
After his success in Malcolm, Frankie made guest appearances in several TV series, such as Sabrina the Teenage Witch, and MAD TV. He eventually landed a few major roles in mainstream films such as My Dog Skip, Racing Stripes, and Agent Cody Banks and its sequel.