Marina Sirtis talks about Deanna Troi and the inverse relation between cleavage and brains in TNG
There are certain rules in Hollywood. One of the rules is not written anywhere, but you just know: if you’re doing an action-adventure show, you gotta have chicks on the show for the boys to look at when they’re not blowing up other spaceships. Second rule: if the chick has a cleavage, she cannot have a brain.
So, [after wearing a uniform in the first episode] I got a cleavage, and all my gray matter departed. Which was sad, because originally (I know this is gonna shock you), Troi was supposed to be the brains of the Enterprise. So when the cleavage came, all that left, and I became decorative, like a potted palm on the bridge.
Then of course came the second season, and I was the only young one left. We had me and we had Diana, and so I had to become all things to all men. And so I got the red outfit, and and then we got the lilac outfit and then we got the green dress. Under the green dress I got to wear a corset, a satin corset, with bones in, like Scarlet O’Hara.
Now, as you know, with a corset everything gets pushed up or down. What was pushed down was kind of enclosed in the skirt and what was pushed up was enclosed in what I named “the Industrial Strength Starfleet Brassiere”, which was a wonder of modern engineering. I mean, I used to take it off at night and go "oh blimey, where did they go?". In fact, we had guest stars - and I’m no Twiggy - who would come and see me in the morning as Marina and then they would see me two hours later as Troi, and they’d go to costume and go "I want that bra!"
So then we got to season six, and there was the episode “Chain of Command" where we were trying out the new captain, Captain Jellico (just in case Patrick wanted too much money for next season, we were auditioning other captains), and he said to Troi “Go put on a uniform”. And lo and behold, there was one in her closet. So I put it on, and by then I was skinny, and the director and all the producers were like "she looks good in that, why wasn’t she been wearing that for the last six years?"
So I started to wear my spacesuit. I was thrilled to finally be in a spacesuit. First of all, my pips - cause I had a rank, you know. And then, it was very flattering actually, it looked really good.
Suddenly, I was smart again. My cleavage had gone. My gray matter came flooding back. I was on away teams! I was the leader of one away team! I had a medical tricorder! And unlike Beverly, I seemed to know what was wrong with people.
And, in this one particular episode, where we were on the Romulan ship - because suddenly I am the expert in Romulan technology - I had this line: "That’s impossible. The Romulans use an artificial quantum singularity as their power source". Who did I say it to? Geordi and Data! They didn’t know this. To be honest, when we were shooting the scene and I was saying the line, I was sneaking looks to my right and left to make sure they hadn’t developed a cleavage while I wasn’t looking.
~ The brilliant and hilarious Marina Sirtis at DragonCon 2010: Star Trek TNG Panel (Abridged from this video. The panel begins here, go check it out, it’s totally worth it).