David Letterman and Robert Downey Jr. talk to lamas in 'My Next Guest Needs No Introduction' trailer
David Letterman sets Lizzo, Kim Kardashian for My Next Guest season 3
All four episodes of season 3 will premiere on Netflix this Oct. 21.
Jimmy Fallon says David Letterman post-9/11 inspired him to do Tonight Show from home
Fallon remembers turning to the veteran late-night host while still an SNL cast member after the Sept. 11 attacks.