The Marx Brothers on Feb 18, 1957, in the green room of America After Dark.

From left: Harpo, Zeppo, Chico, Groucho and the obscure Gummo. Gummo was in their vaudeville act, but left to enter the army in 1918 and never returned to the act. (He stammered, and never liked performing to begin with.)

Chico, the oldest, was about 14 years older than Zeppo, the youngest. The first four brothers were born in rapid succession (1887, 1888, 1890, 1892), then there was a nine-year gap before Zeppo came along.

America After Dark was a short-lived format change for the Tonight Show, after Steve Allen had moved on. NBC made it kind of a nighttime version of the Today show. It bombed. Within months, NBC hired Jack Paar and went back to the old Tonight Show format.

There was also a transition period in 1962 when Paar left. NBC hired Carson, but Johnny was under contract to do a game show on ABC, so NBC filled in for Paar with various guest hosts for a few months. In that interregnum, they retained the Tonight banner and format.