Robert Downey Jr.
Robert Downey Jr. started his career at just five-years-old. He starred in Pound, which was a movie that was both written and directed by his father. If it weren't for his A-list parents, Downey Jr. probably wouldn't be in the place he is today. Downey Jr. starred in dozens of hits in the 1980s, but he struggled to remain relevant in the 2000s until he was cast as Iron Man.