Ok, I know not a pun but funny anyway....
A man and a woman who had never met before, and were both married to other people, found themselves assigned to the same sleeping room on a Trans-continental train. Though initially embarrassed and uneasy over sharing a room, they were both very tired and fell asleep quickly..... He in the upper bunk and she in the lower.
At 1:00 AM, the man leaned down and gently woke the woman saying, "Ma'am, I'm sorry to bother you, but would you be willing to reach into the closet to get me a second blanket? I'm awfully cold."
"I have a better idea," she replied . "Just for tonight, let 's pretend that we're married."
"Wow! That's a great idea!" he exclaimed.
"Good," she replied. "Get your own fuckin blanket."
After a moment of silence, he farted.