If you're at Hollywood Studios (I still have to pause and catch myself from saying MGM Studios...) and looking for a truly unique dining experience, consider checking out the Sci-Fi Dine-In located on the Hollywood Studios Backlot. This restaurant definitely has one of the most unique interiors of any Disney restaurant and one that is sure to amuse kids and adults alike. The restaurant is set-up as a 1950s drive-in theater complete with a nighttime sky, a big movie screen showing kitschy 50s and 60s Sci-Fi monster flicks and tables that are actually convertibles that you sit in to eat your meal. You'll feel like you just drove right on up to catch the movie!
This was definitely a favorite restaurant of mine growing-up.
If you do decide to dine at Sci-Fi, here's a tip you might find useful - bring a small penlight/flashlight or have a flashlight app on your smartphone - it's very dark inside the restaurant and the menu can be very difficult to read without additional light. You can always check out the menu beforehand over at AllEars.net to get a idea for what you'd like, too. The restaurant has recently gone to a new all-day menu that has seen some of the classic items (like the black and blue steak salad) removed, all though some favorites, like the BLT Soup remain. The folks at Disney Food Blog had good things to say about the new menu, especially the burgers. Milkshakes are also a solid choice!
The bottom line: the food may not be the best in the Parks, but it is hard to beat the atmosphere.