Alex Karras, a fierce and relentless All-Pro lineman for the Detroit Lions whose irrepressible character frequently placed him at odds with football’s authorities but led to a second career as an actor on television and in the movies, died Wednesday at his home in Los Angeles. He was 77.

Karras had kidney disease, heart disease and stomach cancer, his family said in a statement announcing his death, as well as dementia. He was among the more than 3,500 former players who are suing the National Football League, in cases that have been consolidated, over the long-term damage caused by concussions and repeated hits to the head.

To those under 50, Karras may be best known as an actor. He made his film debut in 1968, playing himself in “Paper Lion,” an adaptation of George Plimpton’s book about his experience as an amateur playing quarterback for the Lions, which starred Alan Alda as Plimpton.

His rendering of his own roguish personality led to several appearances on “The Tonight Show With Johnny Carson,” and in the 1970s he played numerous guest roles on series television, on shows like “McMillan & Wife,” “Love, American Style,” “M*A*S*H” and “The Odd Couple,” in which he played a comically threatening man-mountain, the jealous husband of a woman who had become friendly with Felix (Tony Randall). Perhaps most memorably, he played Mongo, a hulking subliterate outlaw who delivers a knockout punch to a horse, in the Mel Brooks Western spoof “Blazing Saddles.”