Trivia: When Frank throws water on a waiter he thought was on fire, he apologizes and claims he thought the waiter was Richard Pryor. This is a reference to the time Richard Pryor, while doing cocaine, set himself on fire and ran down a busy street in L.A.
Trivia: Bill Murray slipping out of the restaurant wasn't scripted, he just slipped on wet steps.
Trivia: Frank's brother James is played by Bill Murray's younger brother John. His father is played by Bill's older brother Brian Doyle-Murray.
Trivia: Bill Murray wasn't a fan of Richard Donner's direction, saying "He kept telling me to do things louder, louder, louder. I think he was deaf."
Trivia: When Frank is startled by an actor who he thinks is the Ghost of Christmas Future, he elbows his secretary Grace in the face. That was real. Bill Murray really did hit Alfre Woodard by mistake.
Trivia: Director Richard Donner has a cameo as a worker in the control room towards the end of the movie.
Trivia: Scrooge talks to a group of musicians playing around a fire in a barrel on the street. One of them is jazz great Miles Davis.
Answer: It's a vision, not reality, so one could interpret it either way. I think it's more powerful if Calvin is seeing Frank, silently accusing him of being (at least partially) responsible for his (Calvin's) situation.