Speaking of 'Grey's Anatomy' as a source of Zonks, here's a list of the shows which have referred to it. (Removing all talk shows (Oprah, Letterman), game shows ('Jeopardy'), cartoons ('Simpsons', 'Family Guy', 'Tripping The Rift') and variety shows ('Jay Leno Show', 'Saturday Night Live').
'The O.C.' actually links to the show with Dr. Roberts transferring to Seattle Grace Hospital.
MENTIONS OF THE TITLE:
'Notes From The Underbelly'
'10 Things I Hate About You'
"True Confessions Of A Hollywood Starlet"
MENTION OF ACTORS ON THE SHOW
'Psych' - Shawn mentions Patrick Dempsey. In Toobworld, he could be the host of a medical reality show by the name of 'Grey's Anatomy'.
'Nip/Tuck' - Christian referred to the Isaiah Washington situation that led to his departure from the show.
When the Winchester brothers found themselves in a TV universe of their own, they were stuck on the set of 'Dr. Sexy, M.D.'. It was like 'Grey's Anatomy', but no other connection was made.
REFERENCES TO 'GREY'S ANATOMY' NICKNAMES
(Mostly "McDreamy" & "McSteamy")
'The Sarah Silverman Program'
'Degrassi: The Next Generation'
'Two And A Half Men'
AN ACTUAL ZONK?
In the "Operation: Oswald Montecristo" episode of 'The Knights Of Prosperity', a poster for the show is seen on the set for 'Live with Regis And Kelly'. I don't know how closely it resembles 'Grey's Anatomy' the series as we know it in the real world.