1. Jörmungandr is so fat that when she sits around the world, she sits around the world.
2. Jörmungandr is so stupid that she got locked in a grocery store and almost starved to death but then started gnawing on her tail.
3. Jörmungandr is so dumb that she slithered over a glass wall just to see what was on the other side (what was on the other side was Ragnarök).
4. Jörmungandr is so stupid that when Odin's son defeated Fenrir the wolf by putting one foot on his lower jaw and pulling upwards on the upper jaw she said, "But what about his shoe? It'll get bloody!"
5. Jörmungandr is so wimpy that the only two things that didn't promised not to hurt Baldr were mistletoe and Jörmungandr, but Jörmungandr is even wimpier than mistletoe, so Loki didn't even consider using her for his evil plot to slay Baldr.
6. Jörmungandr is so fat that when she disguised herself as Utagarda-Loki's cat, Thor was only able to lift one of her four feet off the ground.
8. Jörmungandr is so stupid that when Thor went on a fishing trip with the giant Hymir and used the head of an ox as his bait, Jörmungandr snapped his great maw around the bait. Jörmungandr didn't realize that "ox head" is not an aquatic animial.
8. Jörmungandr is so dumb that when Thor stabbed her, then walked nine paces and died, Jörmungandr thought that he walked ten paces. Jörmungandr can't count.
9. Jörmungandr is so dumb that he tried to tell a "your mom" joke to Hel without realizing that they were both born of the giantess Angrboda.
10. Jörmungandr is so stupid that when Surtr set the entire world on fire, she plunged the earth into the ocean to put it out, thus ending the world and making way for the new age.
Um, actually, good call on that one, Jörmungandr.
Feel free to use your own extensive knowledge of Norse mythology to write your own Jörmungandr jokes and post them in the comments!