John Belushi met Dan Aykroyd while working at what Comedy club best known as the first ever on-going improvisational theater troupe based in Chicago.
John Belushi:  Throughout his career, Belushi had a close personal and artistic partnership with his fellow "SNL" star Dan Aykroyd, whom he met while they were both working at Chicago's The Second City comedy club. The Second City: The Second City is an improvisational comedy enterprise, best known as the first ever on-going improvisational theater troupe based in Chicago.
The Second City