Chuck wrote
I think a pop-up box is great to achieve a startle effect. Like Alex said, using it more than once in a game is risky. But imagine a character going to sleep.... you put in two pauses, then BANG! A popup box describing a nightmare appears. Close the box and wake up.
You can make a very passable equivalent by showing a picture that looks like a pop up box if you really must. There won't be a working 'OK' button but the player would still have to dismiss the picture.
Actually you could do it with text in the ZAP! - POW! Marvel comic style if you went this way - very startling.
Al