“That’s not really your dog.” Eggarrrhhh!
“I know you’re a drug dealer.” Glarrrppp!
It’s a common convention in television and movies. Someone learns some awful news, and promptly pukes. I most recently saw an example of this technique while watching season two of Weeds (an excellent show, incidentally, and justification enough to include a picture of the lovely and talented Mary-Louise Parker).
I’ve never done it myself, or seen anybody do it, so I’ve always thought of it as lazy writing. It’s a quick and dirty way to dramatize the impact of exposition.
Have you ever vomited upon hearing bad news, or known somebody who has?