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1.
Everyone knows whales have huge penises, they even make the sea salty with all their semen. A slippery sleeping bag is the act of climbing into a whale's penis, cause you'd totally fit.
"So I saw that Bear Grylls where he slept in a dead camel, apparently the desert is cold at night. Weird I know. So anyway, I figured it might work the same with a whale's penis, but I was all wet so I was still cold.

Still though, I'm gonna copyright it, so Bear Grylls can't talk about the Slippery Sleeping Bag without paying out.
by amnsiac May 15, 2009
 
2.
Where you use a whale's penis as a sleeping bag.
JD said: "I think I'm going to go for a sleep in my slippery sleeping bag."

He climbed up through the whales japseye and used its penis as a slippery sleeping bag.
by JFromH May 15, 2009