In the movie Boogie Nights, yes, the huge penis that he whips out at the end is definitely a fake.
However, shortly after the beginning of the film, Mark comes home from the restaurant where he works and goes into his room. He strips and stands in front of a mirror admiring his terrific body. In this scene, he's wearing only a skimpy speedo or maybe it's a pair of briefs, and he's showing quite a nice, large, penis-shaped bulge, which I'm sure, is his own REAL meat!
The story goes that at first Mark was very willing to use his own real dick for that famous last shot of the film, but when he learned how big it was supposed to be, then he agreed to let them use a fake one.
At any rate, he is indeed very HOT!