Ahh, oyako-don... a classic comfort food that will serve as a one-bowl meal. If you like oyako-don enough, you can actually get pans designed specifically for making it. The standard design is a very small, thin, copper pan with a wooden handle that sticks straight up. The lid has a small hole to allow some steam to vent while cooking. The vertical handle allows you to easily slide the topping right-side-up onto the rice for that professional look. Recommended accompaniment: tsukemono and miso soup. Mitsuba also makes a great garnish.
Like all "donburi" dishes, the word "donburi" is commonly shortened to "don". So, if you want to order it like a pro, ask for the "oyako-don". But be careful -- you might not get exactly what you expect.
I once worked at a Japanese restaurant in Canada, and we had a system for the oyako-don. The menu said "oyako donburi", and people who asked for "oyako donburi" got it with the egg fully cooked, per standard Canadian health regulations. We assumed that people who ordered "oyako-don" would appreciate the authentic style, with the egg only partially cooked. This actually worked quite well; complaints about the egg were very rare.
Also, there is at least one other type of oyako-don around. Sometimes known as "kaisen oyako" or "sake oyako-don", this dish consists of salmon sashimi and roe on rice (sometimes sushi rice), often served with a light soy sauce and wasabi. Some kaisen (fresh seafood) and sushi restaurants list this dish as simply "oyako don", with the assumption that their customers will understand that the meat on the menu is fish.
In conclusion, if you're not into raw egg or raw seafood, be sure to check before you order. Actually, it's probably a better idea to stay the hell away from (authentic) Japanese food in general!
re: tokumei's writeup: I disagree; that is most assuredly a slang term, and a rather obscure one at that. A quick search through six seven major Japanese dictionaries didn't come up with a sukebe meaning -- what the hell is wrong with Sanseidou anyways?. I must humbly conclude that tokumei is da man.
UPDATE: Wow, not only Daijirin (Sanseido Publishing), but it's also in Visual Daijiten (Shinseiki). As a non-slang meaning, it says, "Having sexual relations with both a mother and her daughter, or, with both a man and his son." (I guess that's the PC version.) There is also a slang term listed -- in horseracing, when two horses from the same stable or owner come in first and second, it's also called "oyako-don".
I also surveyed my friends, but only my most perverted friend said he'd heard of it in a sexual sense, and he thought it meant incest. The Otaku Translator's Reference Source Dictionary defines it as "Sexual intercourse featuring parent/s and their off spring (sic). It can also specifically refer to sex with both the mother and her daughter, or any other combination." (available online at http://www.tc.umn.edu/~kane0034/otrd/otakdice.htm) Disclaimer: Not a real dictionary.