This was a local chain of diners in the Greater Pittsburgh area. The one I remember was
located in the upper level of Century III Mall (one of four eateries located outside the food court that included Elby's Big Boy, Ruby Tuesday and Ground Round).
The owner, Lou Pappan, was one of these very colorful characters who liked to do his own commercials. He spoke with a very heavy foreign accent (Greek I think). He would promote his specials in a booming voice, and always conclude by saying "And you gonna like it!"
That last bit was said with such force and vigor that it always sounded as if he was threatening you. You're gonna like my food......or else!
Lou Pappan is apparently still alive at age 87. The chain filed for bankruptcy in 2007 after struggling for years. I am told that a Pappan's still exists in the Green Garden Plaza in Aliquippa, PA (the location of the former operations center for Hills Department Stores). Have not been up there lately to verify myself, and if it does exist I don't know what if any relationship it might have to the original Pappan's chain.
(http://bike-pgh.org/wp-content/uploads/2011/12/pappans_family_close.jpg)
https://www.bizapedia.com/pa/pappans-family-restaurants-inc.html
https://www.highbeam.com/doc/1P2-11286010.html
Not sure if this makes it guaranteed, but the 2nd link is about the 2007 bankruptcy and mentions Lou's son Demetrios and the 1st link refers to the Aliquippa location (and shows updated in 2016) with two principals, both named Demetrios, so...
Of course, searching doesn't bring up any kind of website or Facebook page for the restaurant.
This got by me somehow, but Lou Pappan passed away in April at age 92.
https://en.wikipedia.org/wiki/Lou_Pappan