Just another reason not to judge a book by its cover.
As a quite normal looking teen over 15 years ago, I was treated poorly, followed and given horrible service in resturaunts.
One time I took my friend out to lunch at our favorite resturaunt during the week because they had GREAT lunch specials, we barely got any service, I was argued with about my order (I got the same thing everytime, crab cakes and crabmeat au'gratten with a baked potato, she insisted that it came with potato SALAD, which I do not eat unless my mom makes it, and even when I showed her on the menu that it was a baked potato, she continued to argue with me), no refills, and no notice until the check was dropped if in a "drive-by" way, not asking if we wanted desert or anything.
I paid the bill in cash and only had 1 of the 9 dollars of change owed me brought back. When I asked about my change I was told she was "Keeping it for her tip.". The bill was around $21. I asked to see the manager, waited a LONG time to see the manager. When I told the manager what happened, he started to side with the server until I pointed out that a 20% tip on the tab would have been closer to $4.20, and the service we got was not good enough to warrant that, and by keeping my $8, the server was helping herself to my $3.80 because she thought she could get away with it (not the money here, the principal) and that $8 dollars was close to a 38% tip wihich she no where NEAR deserved.
Now, my friends family had gone there for Sunday lunch after church every year for over 5 years, and both he and I knew the owner, but did not pull the "I know the owner card", until the owner walked over and said hello to us, offered us free Bread Pudding (they had the best) and asked what the problem was...
My friend never saw that server or "manager" again (who was actually another server NOT a manager, hard to tell hen they all wear tuxedo shirts, vests, and pants)
And I always tipped well, it was ingrained into me by my parents.