A Bar in Cuba

A Scotsman is sitting in a bar in Cuba and is minding his business when a man with a large black beard walks in.
The man goes to the bar and orders a shot of whisky. The bartender serves him,
the man drinks the whisky then starts walking out the door.
The bartender says, “Hey! Aren’t you going to pay for that?”
The man says, “It’s free. I’m in Castro’s Army.”
The bartender says, “Sorry” and the man leaves.
A few minutes later another man with a large black beard walks in.
The man goes to the bar and orders a shot of whisky.
The bartender serves him, the man drinks the whisky then starts walking out the door.
The bartender says, “Hey! Aren’t you going to pay for that?” The man says, “It’s free.
I’m in Castro’s Army.” The bartender says, “Sorry” and the man leaves.
The Scotsman gets an idea and walks up to the bar and orders a shot of whisky.
He drinks the whisky then starts walking out the door. The bartender says,
“Hey! Aren’t you going to pay for that?”
The Scotsman says, “It’s free. I’m in Castro’s Army.”
The bartender says, “Hey! Where is your big black beard?”
The Scotsman thinks quickly. Then he lifts his kilt and says, “Secret Service!”