The Strongest Man in the World (1975)

Dexter Riley and his friends accidentally discover a new chemical mixed with a cereal seems to give anyone temporary superhuman strength. (imdb)
Genres: Comedy, Family/Kids, Fantasy
Country: USA
Directed By: Vincent McEveety
Written By: Joseph L. McEveety, Herman Groves
Starring: Kurt Russell, Harold Gould, James Gregory, Dick Van Patten, Raymond Bailey, Phil Silvers, Joe Flynn, Benson Fong, Cesar Romero, Eve Arden, William Schallert, Burt Mustin