Cal was a diner patron in Broward, Florida.
Cal was a haggard-looking young man who was among the customers in the diner that was part of a time loop that Sam and Dean became entwined in while investigating the Broward County Mystery Spot. Cal was known to the waitress, Doris, by name and informed by her that he'd have to leave unless he purchased something. He responded by sheepishly sliding some change toward her and ordering a cup of coffee.
As Sam was the only one aware of being trapped in the time loop, he eventually informed Dean of the facts he'd learned about the people assembled at the diner. He revealed that Cal was going to rob the local mechanic on his way home.
After Sam finally sussed out the trickster amongst the diner patrons and threatened him with a blood-dipped wooden stake, he promised he'd end the loop. Sam was relieved to wake up and find it was finally Wednesday, and was eager to get out of town. As Dean was out in the parking lot loading the car, Cal approached him with a gun drawn and demanded his wallet. Back inside the motel room, Sam heard a shot. He ran out to see Dean lying mortally wounded with a gunshot to his chest as Cal ran away.