Big Gerson's is a chain of restaurants with branches all over the United States of America. Different locations have played part in different supernatural confrontations throughout the series.
After Sam gets cursed by the rabbit foot, he and Dean head to the restaurant to kill time while Bobby finds a way to stop the curse. Upon entering the place and asking for a table, the waiter congratulated them for being the one millionth customer and presents them with a big check. With it they get free food for a year, and Sam and Dean's picture was taken. This picture would eventually alert Kubrick and Creedy that Sam and Dean were in town. As Sam and Dean ate, a waitress approached and poured some more coffee for them. She accidentally spilled some on Sam and began to wipe it off. As she left Sam and Dean checked her out. Immediately after, Sam's luck turns sour. The boys then realize that the waitress was actually a thief named Bela, who had been planning to acquire the foot.
A waitress working in one of the branches was suddenly assaulted by harsh truths from the customers and her coworkers. She called her sister to vent her worries, only to hear her sister speak in the same blunt manner as well. In her distress, the waitress shoots herself right in the middle of the restaurant.
On a case with Bobby, they stop at Biggerson's to interview Ranger Rick. Once finished, they decided to grab a bite there as well. Dean ordered a Turducken Slammer, however, Dean seemed to be in a half daze after eating the burger. Later as they autopsy a body, Dean expressed his desire to return and eat again at Biggerson's. There, Dean noisily enjoyed the burger, which give Sam a clue that the burger might be the cause of Dean's odd behavior. Sam also noticed that everyone in the place was also eating the Turducken Slammer. They later checked the delivery truck and find out that the meat used by the restaurants were manufactured by Leviathans.
Castiel used the similar set-up and design of Biggerson's to great effect in escaping angels working for Naomi. He would teleport to other locations of his own pattern and choosing whenever he felt that other angels are closing in on him. To break this, Naomi had her angels kill and fatally wound humans in one location to draw Castiel out. This proved successful, as Naomi managed to track down and interrogate Castiel. Before she could finish, however, Crowley arrived and threatened to kill Naomi, forcing her to flee and leave Castiel to the hands of the demon and the double-agent Ion.