In fact I share the general - and altogether respectable - horror of speaking before audiences of any kind. So my instinct was to decline, politely. But what would my nieces Carmen and Catrina say? Scarier still would be the affronted reaction of my gay friends addicted to the show.

While I would never claim much range as a performer, I was fairly confident that the role of self would fall securely within it. Also, as someone who makes a living assessing the achievements of people who have the courage to risk making fools of themselves every day - to be a good actor is to be fearless about emotional self-exposure - I knew it would be cowardly to say no.

And then there's that whole vanity thing.

Three days later I found myself being picked up at my door for my day of shooting at a theater on Grand Street on the Lower East Side. I had received my sides - that's actor talk for script pages - the day before. I was given three lines in a scene set backstage after a high-school theater performance.

Instantly dashed were my fantasies of delivering some Addison DeWitt-type acerbities, good-naturedly playing into the popular notion of the critic as a viper who cannot open his mouth without savaging somebody or something. The lines I was given were more anodyne. I briefly considered lodging a gentle protest but figured it would be a little immodest to request that my lines - all three of them - be guest-written by the staff of "30 Rock."

The first shock, after the small frisson of being chauffeured to the set (it was a van, but still), came when I discovered I would be given my own trailer for the half-day or so of shooting. My name was even on the door (scribbled on a bit of blue tape, but still). That's when things began to turn slowly and inexorably wrong.