The gallery has acquired portraits of Vegas, Matt Lucas, Jimmy Carr and other comedians as part of a display charting 70 years of British comedy heroes.
More than 50 photographic portraits of comedians from the 1940s to the present day have gone on display at the London gallery.
Vegas was photographed, mimicking Moore's 1991 naked while pregnant pose by Annie Leibovitz for the cover of Vanity Fair, by Karl J Kaul.
The display includes the likes of Kenneth Horne, Eric Sykes, Tony Hancock, Sid James, Spike Milligan, Catherine Tate and Ricky Gervais.
Comedians: From The 1940s To Now runs to January 2 at the National Portrait Gallery.
Johnny Vegas as Demi Moore by Karl J. Kaul © Karl J. Kaul