Van Dyke certainly did that. He took drama classes at high school, and after leaving, he ended up with an unusual job in the army. He became an announcer on the radio, and then a Special Services entertainer for the troops. However, the future star was never permitted to serve in combat, because he was underweight at the time.
When Van Dyke made it into the acting business, it was in a big way. He played the lead in Bye Bye Birdie on Broadway in 1960, despite having had no previous dancing experience. That performance won him a Tony. The actor then went to TV and The Dick Van Dyke Show. And while appearing in that series, he nabbed the part in Mary Poppins.
Walt Disney personally chose the actor, in fact. “I thought he hired me because I was such a great singer and dancer. As it turns out, he had heard me in an interview talking about what was happening to family entertainment,” Van Dyke told CNN in 2009. “That’s why he called me in, because I said something he agreed with.”