Heh.
Seriously: I have a vague memory confirming the Daryl Hannah potato-in-the-lobster-shell workaround. I have an even vaguer memory about the need to wash the shell really thoroughly beforehand, and she still didn’t enjoy doing it.
Ah, Art.
Very similar is Dead Again, in which Kenneth Branagh’s smoking habit is continually referred to but he’s never actually seen with a lit cigarette in his mouth. Later we see Andy Garcia, playing an 80 year old chain smoker,
[spoiler]smoke a cigarette through his stoma*
which I took to be a “but seriously folks, smoking is bad” moment.
Re: the “coughing” audience member: I was in a production of Night of the Iguana once in which the same thing happened- about three audience members started coughing when the character Shannon lit up. The irony is that the actor was using the “powder smoke” cigarette.
Of course I quit smoking for three years and blame smoking a cigar in a play for my return. (Cigars make you crave cigarettes like nobody’s bidness.)
Cervaise will correct me if I’m wrong, but that wouldn’t necessarily change even for an actor who loves lobster. I understand that when an actor must be filmed to eat something, they sometimes employ a spit bag off-camera so they don’t get filled up with food on the first few takes.
It would be a more common technique where a commercial of some tasty füd produkt is being filmed, for instance, or for a long dinner scene with many people at the table—what with multiple takes from different angles, an actor would have to eat on every take. That’s a lot of food.
William Shatner talks about how difficult it is to film scenes with food on the documentary disc of “Star Trek VI.” Very often, actors in film “eat” the way non-smoking actors “smoke.” Raise fork, act as if to eat but instead say your line, cut away to other actor. Repeat as necessary. Shatner claims that the director Nicholas Meyer bribed the actors something like $25.00 per take if they ate on-camera.
Fish is correct. When it comes to filming scenes about eating, actors much more frequently spit than swallow. 
Cervaise, can you give us a link to your website with the movie reviews? And have you yet reviewed Almost Famous?
Regarding fake marijuana smoke, I must have seen your college production. While reading the article I was reminded of a play I saw when I was living in Chicago over 10 years ago: a very small production of Marijuana, a satire on an anti-marijuana film from the 50’s. As the stage was small, we could smell what we swore was pot from the actors. We had diner with one of the actors after and he told us they were smoking oregano!