Karras, who was nicknamed "The Mad Duck," was born in Gary, Ind., and played football in high school and later for the University of Iowa. In 1958, he was drafted in the first round by the Detroit Lions. He played as a defensive tackle for Detroit from 1958 to 1970, but missed the 1963 season because of a gambling controversy.
After his NFL career was over, Karras pursued acting full-time. Some of his more memorable roles included Mongo in Blazing Saddles, who punches a horse; the sheriff in Porky's and a closeted bodyguard in Victor/Victoria. In the 1980s, Karras became a television staple as George Papadapolis, the adoptive father of the titular boy in Webster (Emmanuel Lewis). Karras and his wife in real life, Susan Clark, played a couple on the series, which they also produced.
Karras was elected to the Iowa Sports Hall of Fame in 1977 and the College Football Hall of Fame in 1991.
In recent years, Karras had battled heart disease, kidney disease, stomach cancer and dementia, according to the spokesperson.
In April of this year, he was the lead plaintiff in a lawsuit filed against the NFL on behalf of 70 former players, alleging that the league didn't do enough to warn players about the risks of permanent brain damage as the result of playing after a concussion. The lawsuit claims his dementia was the result of the numerous head injuries he suffered throughout his football career. (In total, more than 2,000 NFL players have sued the league for similar claims.)
Karras was reportedly surrounded by Clark and his children at the time of his death, after having been released from a California hospital where he was being treated for kidney failure earlier this week.