Today brings together two glorious occasions: Animal House Friday, when one lucky commenter will win a pet-themed prize, and National Hairball Awareness Day.

I ask: If you have a cat, how can you be unaware of hairballs? You hear them on their way up -- the hacking, the coughing, the feline distress signals. Or you're walking along, say, headed to the kitchen and you spot one. Worse yet, you don't see it and (gross-out alert) step in it.

Hairballs are actually called trichobezoars. These nondigested masses are found in animals other than cats, including horses, chickens and cows, as well as humans. They occur when something (food, medicine, hair) can't make it through the narrow opening between the stomach and large intestine.

Here's where it gets interesting: You can learn the truth about hairballs at an exhibit and "hands-on activity" at the National Museum of Health and Medicine in Washington on Monday (April 27) at noon. Visitors that day will, are you ready, "have the opportunity to handle an actual hairball," according to the museum's Web site. (For more details, click here.)

The exhibit is up through May 4, but if you can't make it, there's a virtual hairball exhibit on the museum's site. You can see it by clicking here. I've checked it out, and here's some advice: Avoid around meal time.

Have a hairball story to share? A solution to the problem in your cat, horse or cow? Or simply want to weigh in on why someone would go to a museum to touch a hairball from a chicken? All comments welcome (even off-topic ones). Remember: It's prize day. Comment below and your name will be entered in a drawing for a nifty gift. I'll draw the name at 3 p.m. Please include your e-mail so I can contact you if you're today's winner. (The e-mail will remain private; we just need it to reach you.)

Oh, and (cough, cough) Happy Hairball Day.

Photo: Baltimore Sun Staff Photo by Karl Merton Ferron