You never know which little role is going to lead to the first big one.
Here are the defining moments that helped 11 stars of classic TV shows to land their first major breaks.
Mary Tyler Moore was remembered by a casting director as "the attractive girl with the button nose...and three names."

Mary Tyler Moore had fired the imagination of many TV-viewing young men in the late 1950s when she had a small recurring role on Richard Diamond, Private Detective. Only her sultry voice was usually heard, although there was occasionally a shot of her lengthy dancer’s legs or a profile of her lips as she spoke.
Moore auditioned for the role of Danny Thomas’s daughter on Make Room for Daddy, and while Thomas was impressed with her acting, he ultimately turned her down because “no one would believe that someone with that cute button nose could be related to him.” However, when his production company was casting The Dick Van Dyke Show and an actress was needed to play Laura, Thomas remembered the attractive girl with the button nose and ordered his assistant “get me that girl with the three names.”
Lucille Ball got her start in comedy when she starred in a radio show called "My Favorite Husband (1948)."

Lucille Ball had been appearing in minor roles in a string of B-movies since the 1930s, often as a blonde chorus girl. It wasn’t until 1948 when she landed the role of housewife Liz Cooper on the radio show My Favorite Husband that she’d found her niche—comedy.
After 124 episodes on radio, CBS decided to bring My Favorite Husband to television. The only problem was they wanted Richard Denning, Lucille’s radio husband, to continue the role on TV, whereas Lucille refused to have anyone but her real-life husband Desi Arnaz play the part. CBS eventually hired two other actors to play Liz and George Cooper, but the network still thought that Ball had solid TV potential with her brand of physical comedy, so they eventually relented and gave the green light to a Desilu-produced series called I Love Lucy.
Dick Van Dyke got poached from his Broadway role in "Bye, Bye, Birdie" to star in the sitcom "Head of the Family."

When Carl Reiner submitted the pilot of his proposed sitcom Head of the Family, executive producer Sheldon Leonard liked everything about it except one small detail—Reiner himself. Leonard felt that Reiner was more of a “gag man”—a comic who was just reeling off a series of jokes—than an actor that could carry a sitcom. He also felt that Reiner was too ethnic (read: Jewish) to play white bread, affable Rob Petrie.
Someone had mentioned this guy Dick Van Dyke who could apparently act, sing, and dance and was appropriately middle-American-looking. Leonard went to Broadway where Van Dyke was performing in Bye, Bye, Birdie and decided he’d found their new Rob Petrie.
NOW READ: 5 Remarkable Things Discovered Under Parking Lots >
See the rest of the story at Business Insider