Playing both defensive line and offensive tackle at Lincoln Northeast High School in Lincoln, Nebraska, Danny is considered to this day one of the best in the history of Nebraska high school football players[by whom?]. He was picked to play in the state’s 1983 All-Star Shrine Bowl football game played at the University of Nebraska Memorial stadium.
Noonan was recruited by the University of Nebraska and played as a defensive end during his freshman year. During his junior season, defensive coordinator coach Charlie McBride moved Danny to defensive nose tackle. His senior year, he won numerous awards and honors, including the Big 8 Athlete-of-the-Year, First-Team All-American (AP, UPI, FWAA, Kodak, Walter Camp, Football News) All Star Japan Bowl and Big 8 Player-of-the-Week (Florida State). Danny was also named the game's Most Valuable Player in the 1986 Sugar Bowl. He was coached at Nebraska by Tom Osborne the most successful and highly regarded coaches in college football history. He is a member of the Nebraska Football Hall of Fame. In 2005 Danny was selected by the Omaha World-Herald as one of Nebraska's Top 100 athletes.
Noonan was the Dallas Cowboys' first pick in the 1987 National Football League Draft, and was moved to defensive tackle, where he was a backup to Cowboy legend Randy White. He played for six seasons, playing for the Dallas Cowboys from 1987 to 1992 and for the Green Bay Packers in 1992 and Denver Broncos in 1993.
Noonan's best year statistically was in 1988, as he ran back an interception for a touchdown and recorded 7.5 sacks. Noonan was named All-NFL Strength Team in 1990. He would retire in 1993 with the Denver Broncos.
Noonan married his wife Julie Noonan in 2002. They have five children, Sydney, Sam, Maverick, Alec and Branson. He graduated from the University of Nebraska with a Bachelor of Science Degree and has an MBA from Columbia Southern University with a concentration in E- Business and Technology. Noonan is President of the NFLPA (National Football League Players Association) retired player chapter in Nebraska and organizes visits to the children’s hospital in Omaha with current and former NFL players.