Must say, I think this is an excellent concept! You could end up with a really good script!
As far as the script itself goes, the writing isn't bad, some things could do with fixing (breaking up some of the lines of action, fixing a few spelling mistakes, etc...), but this is certainly a good start.
I agree with Fantasy, the opening scene doesn't work. We're instantly given the characters sat at the table talking, it's not much of an introduction...
At first, I was slightly confused. I thought we were looking at people in costume, not the actual monsters. Just before Walters first line, you've written "The creature from the black lagoon turns around...", it should be "Walter turns around...". This just confuses things even more.
When you introduce a character, put the name in CAPITALS, then give us a brief description, help us to picture them. Sure, everybody can picture what Dracula looks like, describe him anyway, flesh him out for us. Perhaps something like... "Sat next to Dracula is WALTER, a scaley, green fish-man, with a wide mouth full of needle sharp teeth and gills where his ears should be. He looks exactly like The Creature from the Black Lagoon." This could help sell the idea that they are the actual monsters. Also, are they old now? Maybe Dracula is bald? Maybe the Wolf-Man's thick brown coat has started to go grey? Just a thought.
One more thought, get rid of Merlin. He doesn't fit with the others. The rest are Universal monsters, Merlin's a mythical wizard, they don't sit well together for me. Change him for The Invisible Man, or the Phantom of the Opera, or Dr. Jekyll and Mr. Hyde... somebody else that has appeared in Univerals monster movies. Or just get rid of him full stop, the five other work perfectly together. Just my opinion...
Good luck, this is a great start!
