That's here on CBS, where the 'C' stands for 'Classy' and the 'BS' speaks for itself.

This line is a characteristically self-deprecating, meta-network joke in which Ferguson riffs on the CBS acronym to puncture the supposed “classiness” of broadcast television. By declaring the “C” to mean “Classy” while letting “BS” “speak for itself,” he simultaneously flatters the network’s prestige branding and undercuts it with a blunt insinuation of “bullshit.” The humor depends on the audience’s awareness of late-night TV’s constant negotiation between corporate respectability and irreverent comedy, and it showcases Ferguson’s persona: charming, mischievous, and willing to mock the very platform that employs him.