Before his razor-sharp wit made him a late-night television sensation, Arthur "Fatso" Donovan Jr. established himself as one of the most destructive interior defensive linemen in the early history of professional football. A World War II Marine Corps veteran who saw combat at Luzon and Iwo Jima, Donovan joined the original, short-lived Baltimore Colts as a 26-year-old rookie in 1950. When that franchise dissolved, his early career took a bizarre path: he played for the New York Yanks in 1951 and the Dallas Texans in 1952, earning the unique distinction of playing for three consecutive franchises that folded in back-to-back-to-back seasons.

Donovan's wild journey stabilized in 1953 when the NFL awarded a new franchise to Baltimore, purchasing the defunct Texans' assets and returning the stout defensive tackle to Maryland. Anchoring the interior alongside Gino Marchetti and "Big Daddy" Lipscomb, Donovan weaponized a 263-pound frame, tremendous leverage, and an uncanny ability to diagnose plays before they unfolded. Known for his relentless motor and "bulldog" tenacity, he earned five consecutive Pro Bowl selections from 1953 through 1957 and four straight First-Team AP All-Pro selections from 1954 through 1957.

Donovan's peak coincided with the franchise's rise to the top of the gridiron. He was the defensive anchor for the historic 1958 and 1959 Baltimore squads that captured back-to-back NFL Championships, including the iconic 1958 title game victory over the New York Giants—widely celebrated as "The Greatest Game Ever Played". Beyond his on-field destruction of opposing ground games, Donovan served as the heart and soul of the locker room, utilizing his legendary storytelling and infectious humor to keep teammates loose during high-stakes championship runs.

After retiring in 1961, Donovan was honored on the NFL 1950s All-Decade Team. In 1968, he became the first Baltimore Colts player in the Hall of Fame. The Colts retired his No. 70 jersey, cementing his key role in franchise history.