Starring: Kelsey Grammer, David Hyde Pierce, John Mahoney, Jane Leeves, Peri Gilpin
Roz's Turn - S4-E17
Revealing mistake: Bebe is in the booth telling Frasier how she misunderstood him about Roz. As she says "wink", we can see Frasier's reflection in the booth's glass - his head bobs up. The next shot we see, though, is of Frasier's head bobbing up - shot at the same time, we just see it a split second later.
Visible crew/equipment: When Frasier is standing through his sunroof to speak with the drivers stuck behind him in the parking garage, one shot shows Frasier's body and much of the rear window which features a very clear reflection of the boom mic.
Selling Out - S1-E9
Frasier: Roger, at Cornell University they have an incredible piece of scientific equipment known as the Tunneling Electron Microscope. Now, this microscope is so powerful that by firing electrons you can actually see images of the atom, the infinitesimally minute building blocks of our universe. Roger, if I were using that microscope right now, I still wouldn't be able to locate my interest in your problem.
Chosen answer: The turkey's stuffing.