How Loki let a horse fuck him all night for a wall.

Once long ago the Norse gods wished for a wall to be built around Asgard to defend against beings and monsters other than the Ice Giants.  They didn't have the capacity to make it on their own in the amount of time they wanted (lazy) so they sought out to hire somebody who actually was willing to do it.  The one man they found for the job said he and his magical horse could make such a wall, yet demanded the moon in payment.

The gods were fairly skeptical of the man's claims, to which he convinced them by accepting payment only once the last brick was laid and immediately began at work like he said.

Flabbergasted at the man and horse performing masonry together, the gods let the magic stallion carry on its work while they tried to think of some way to squeak out from giving him such an important object as the moon.

This is when Loki comes in with a unique idea.  He started explaining from the conditions of the man's wall around Asgard that the gods only had to give him payment if he finished the job.  They wait until the night before the day the wall should be finished and let Loki shapeshift into the most beautiful mare he could to entice the stallion away from his job until the next day, when the man showed back up to see his wall unfinished and his horse gone.  After the gods basically went "aw that's too damn bad, you had a deadline" the horse shows back up from the forest to leave with the man, while the gods finished the wall themselves.