Why do people have costume parties?

So this fellow is turning forty (40) and he wants a costume party.

So the beloved of my heart, mother of my children, Beast of Brisbane, Hammer of the Helpless, decided to let out her inner Morticia. Knowing the calibre of the other guests, I decided to be prepared as a Fearless Vampire Killer.

The "walking stick" is actually a concealed stake-cane. Note the narrow-eyed look of suspicion. You can tell we're married. This posting is for the amusement of Quokka, Morgana, Catty et al and should not be read by anyone else. Especially NowhereBob.