Media personalities who team up with each other very often, to the point they become inseparable in the public eye.
The American Quartet
The Brat Pack
The Firesign Theatre
The Frat Pack
The Happiness Boys
The Marx Brothers
The Muppets performers. Especially Jim Henson, Frank Oz, Jerry Nelson, Dave Goelz and Richard Hunt.
There were regular double acts within the Muppeteers, most obviously Henson and Oz (Kermit and Piggy, Kermit and Fozzie, Ernie and Bert) but also Nelson and Hunt (Floyd and Janice, Robin and Sweetums, the Two-Headed Monster, Pa and Junior Gorg), Goelz and Steve Whitmire (Gonzo and Rizzo, Andy and Randy Pig, Stinky and Jake from The Animal Show, Mew and Rugby, Boober and Wembley) and more recently Brian Henson and Bill Baretta ( Seymour and Pepe, Sal Minella and Johnny Fiama and Sampson and Bobby in the short lived Henson Alternate series Tinseltown).
The Rat Pack
The Royal Shakespeare Company (throw a metaphorical dart at your average group of British actors over thirty. 99% of them put in a stint at the RSC.)
The Three Stooges
Edgar Wright, Nick Frost, and Simon Pegg.
Double Act, Comedy Duo