It may seem like a harmless bit of fun to share a bed with a lobster, but there are actually some dangers associated with it. For one thing, lobsters are not particularly clean creatures. They live in the ocean, where they are constantly exposed to all sorts of bacteria and other harmful organisms. If you were to sleep with a lobster, you would be exposing yourself to all of those same organisms.
In addition, lobsters are very sharp creatures. They have large claws that they use to catch their food. If you were to roll over in your sleep and accidentally get one of those claws caught in your skin, it would likely result in a pretty nasty cut.
Finally, it should be noted that lobsters are not exactly cuddly creatures. They are not known for being particularly affectionate, and they may even view you as food. So, if you are looking for a cuddle buddy, a lobster is probably not the best choice.