I used to frequent this place a lot as a freshman at CMU down the street-- mostly because we had money on our food dining card and it could be used for ENP. This ENP is really easily accessible by the public buses that go from CMU to Squirrel Hill.
Granted, this ENP is kinda old and could use some re-decorating (it feels like a blast from the past) but if you want OK/decent diner food for OK/decent prices, ENP is an option... I think some of their food was kinda greasy, and I remember a sandwich was that positively drowned in gravy.
I do recall that their shakes are actually pretty good. I remember getting one that was mocha and it had an espresso bean on top of the whipped cream. Totally didn't sleep that day.
Their smiley cookies are also good here too. They're just plain sugar cookies with icing on the top and their silly face drawn on it - I mean you could get these iced cookies in the supermarket too but don't you want the smiley? So happy!