How a polite "No, thank you" escalates into "Leave me the hell alone!"

I got the e-mail when it came around work.
Our station's booth at the upcoming business expo will feature video fun from YooStar, and all employees are invited to record a scene or two.
Invited.
Invited.

I browsed the site, peeked at some scenes, and decided this is not something I wanted to do.  In public.  On line.  Possibly not ever.
So, I deleted the e-mail.
Because, as you may recall, I was merely invited.  Not required.

Days later, the chick in charge of the booth was hovering outside the studio while I was on the air.  Not gawking, which is rude and distracting.  Hovering.  Just to the side of the studio window.  Which is rude and distracting.
She snagged me as I was leaving for lunch.
"You wanna come down and see our karaoke?"
"Um.  No."
"Oh, c'mon.  It's fun!"
"Um.  No."
"But why not?  It's fun!"
"No.  Really, I'm not interested."
"Well, just come look and see what everyone else is doing."
Sigh.  "Okay."

All the way down the stairs, she laid on the too-much-caffeine description of how much fun it is and how everyone is drinking the Kool-Aid and wouldn't it just be fun!
"I saw the e-mail," I told her.  "I looked at the YouStar site.  I'm really not interested."
"Mike is there right now," she bubbled.  "He's really good.  And he's having fun!"

As we approached the video area, the computer tech shouted out, "Hey!  Is she gonna do the Ferris Beuller clip?"
"No."
"Aw, c'mon.  It's fun!" This one is Mike.
"I am not interested."
"But why not?"
(Insert several rounds of "You can do this one..." "No." "...or this one..." "No.")

Finally, it happened.
"Aw, c'mon. Just sit over here and we'll just..."
"You know what this reminds me of?" I interrupted. "This is just like that time when I was a kid and my mom dragged me to the dentist office. I didn't want to go. I hid in the lobby. They kept trying to make me go in. And the nurse says to me that I just have to sit in the chair. It'll go up and down, she says. So, I say okay, I'll sit in the chair.  AND THEN THEY DRILLED MY FACE!"

Several moments passed in silence.

But no one asked me which damned clip I wanted to do after that.

***

Funny, I thought I'd made myself pretty clear from the beginning.