"Can I have you for dinner?" asked Martini.
Luke had never been on a date before. He said, "Sure."
Luke spent all day preparing for dinner with Martini. He wanted to look his best. He wore a nice suit and rented a limousine. He rang the doorbell. Martini's house was wonderful and expensive.
"Come in," said a voice.
The two sat down at the dinner table. Martini picked up her fork and knife. Then, suddenly she jumped across the table at Luke.
"What are you doing?" hollered Luke.
"I told you, I was going to have you for dinner!" said Martini.
...
-How often should surprises and plot twists occur in a game story? Is there ever a limit?
I have played Kid Icarus: Uprising and pretty much everything in the story is a twist. I loved it but they could have cut down on the twists and the element of surprise would have been better.
Jeff Vogel (of Spiderweb Software) thinks you should "never write a wacky surprise ending again" and explains his position quite well.
I think there's a place for clever and well-written plot twists, but that they're often just lazy or uninspired writing. Jeff raises a good point about being unable to properly build trust whilst effectively lying to your players in order to set up a twist.
Unless you're going for a particularly funny and light-hearted game I'd probably avoid multiple (large) twists in a single game.