Number of times Johnny Carson appeared on The David Letterman Show after his retirement:

In contrast, Carson never appeared on the The Tonight Show With Jay Leno, his designated successor.
Source: Pittsburgh Post Gazette, 2/1/2005

EditorB (flickr 2006)
Amount David Letterman reportedly makes to host "The Late Show":

$35 million
While New York Post reported on Dec. 5, 2006 that Letterman entered into a contract which will pay him $35 million annually, the Feb. 27, 2008 New York Times reported that Letterman is paid "more than $30 million" annually.
Source: New York Post, 12/5/2006

Zac-Attack (flickr 2006)
Amount Jay Leno reportedly makes annually to host "The Tonight Show":

$26 million

Source: New York Post, 12/5/2006

  Andy Samberg's debut on SNL:

Oct. 1, 2005
Before joining SNL, Samberg produced comedy videos on and their own site, His first SNL sketch was in a parody of a Morgan-Stanley investment commercial.
Source: USA Today, 9/30/2005