The Party Store Is Just A Michigan Thing
So, if you're reading this in Michigan (well okay, I know what you're gonna say if you live in Michigan) or anywhere in the great big beautiful country of ours, you probably have a name that is regionally exclusive to that little corner (or maybe not on the corner) store that you always go to pick up various items like, well...beer and liquor and other stuff.
In Michigan, that little store is called what? You know it...a "party store". You know, what some people would call a convenience store.
Where I come from, that little store was (and maybe still is...) called a "pony keg". Now this same place where I'm from, a pony keg can apparently mean not only a little store, but also a building which serves as a drive-thru where you can get, well...beer. You can also get pop, ice, maybe nuts and chips, too. It's been awhile since I've been to a beer drive-thru. By the way, "pony keg" really is a quarter barrel of beer. I didn't know when I was a kid that was what a pony keg really was when people called a store a pony keg. But as I got older, I knew you could buy a pony keg at the pony keg. What you can't get at the pony keg where I'm from is liquor. You have to get that at the "State Store".
According to Urban Dictionary, that "party store" name is exclusive to The Mitten. In fact, here is what Urban Dictionary says:
Michigan slang term that describes a small convenience store that sells soda, beer, liquor, snacks such as potato chips and hot dogs, and some household goods such as plastic cups and paper plates.
So there you go. A "party store" can be a "pony keg" and vice versa. They are really the same structures for the most part but here in Michigan, party store it is! Here's more info from Urban Dictionary.