Didn’t Humphrey Bogart start the Rat Pack with Sinatra?
“The Rat Pack was an informal group of entertainers, the second iteration of which ultimately made films and appeared together in Las Vegas casino venues. They originated as a group of A-list show business friends who met casually at the Los Angeles home of Humphrey Bogart and Lauren Bacall.[1] In the 1960s, the group featured Frank Sinatra, Dean Martin, Sammy Davis Jr., Joey Bishop, and (before falling out with Sinatra in 1962) Peter Lawford, among others. They appeared together on stage and in films in the early 1960s, including the films Ocean’s 11,[2] and Sergeants 3; after Lawford’s expulsion, they filmed Robin and the 7 Hoods with Bing Crosby in what was to be Lawford’s role. Sinatra, Martin, and Davis were regarded as the group’s lead members after Bogart’s death.[3][4]
The name “Rat Pack” was first used to refer to a group of friends in New York,[5][6] and several explanations have been offered for the name. According to one version, Lauren Bacall saw her husband Humphrey Bogart and his friends returning from a night in Las Vegas and said, “You look like a goddamn rat pack.”[5] “Rat Pack” may also be a shortened version of “Holmby Hills Rat Pack”, a reference to the home of Bogart and Bacall[5][6] which served as a regular hangout.
Visiting members included Errol Flynn, Ava Gardner, Nat King Cole, Robert Mitchum, Elizabeth Taylor, Janet Leigh, Tony Curtis, Mickey Rooney, Lena Horne, Jerry Lewis, and Cesar Romero. According to Stephen Bogart, the original members of the Holmby Hills Rat Pack were Frank Sinatra (pack master), Judy Garland (first vice-president), Sid Luft (cage master), Bogart (rat in charge of public relations), Swifty Lazar (recording secretary and treasurer), Nathaniel Benchley (historian), David Niven, Katharine Hepburn, Spencer Tracy, George Cukor, Cary Grant, Rex Harrison, and Jimmy Van Heusen.[5][6]”
https://en.wikipedia.org/wiki/Rat_Pack