")[4] Aaker appeared on television as a young child, and landed uncredited roles in motion pictures beginning at age eight, in films such as The Greatest Show on Earth (1952) and High Noon (1952).

In 1953, Aaker co-starred in the John Wayne western classic Hondo (1953), as the curious blond son of homesteader Geraldine Page.

Two weeks later, Aaker won the role of "Rusty" on The Adventures of Rin-Tin-Tin, co-starring James Brown (1920–1992) as Lieutenant Ripley "Rip" Masters.

[1] According to Paul Petersen, an advocate for former child actors, Aaker experienced poverty toward the end of his life, and had struggled for years with substance abuse.

Petersen said Aaker had suffered a stroke and died in Maricopa County, Arizona, near the city of Mesa, on April 1, 2021, and was listed as an "indigent decedent".