Thing probably wasn't doing Morticia's makeup, but it was still quite heavy-handed. Start with a foundation a shade or two lighter than your natural skin color, like CoverGirl's Aquasmooth Compact Foundation ($8), and sweep Almay's Clear Complexion Powder ($11) in Light on top. Use the darkest eye shadow pencil you can find, like Rimmel's Professional Eyebrow Pencil ($3) in Black Brown (or any black eyeliner you have on hand) to fill in your eyebrows. Go ahead and exaggerate their shape both up and out--this is the one time it's okay to look like your eyebrows are drawn on.
Don't invest in a fancy frosted eye shadow, instead coat your lids with Wet 'n Wild's Mega Shimmer Dust ($3) in Lotus and use Sonia Kashuk's Jet Set Liquid Eyeliner ($6) in Black to line your entire eye, dragging it out into a dramatically sexy cat eye on top. Use an eye shadow brush to apply Bobbi Brown's Eyeshadow ($20) in Slate across the middle of the lid and pile on as much Maybelline Great Lash Mascara ($4) in Black as you possibly can on both the top and bottom lashes.
Sephora's Crème Lip Stain ($12) in Always Red stays on for 12 hours, meaning you can eat candy or people (depending on just how in character you get) all night long. The best part about Morticia's goth-meets-sexpot look is her nails. They're long, sharp, and blood red, the better with which to chastise Wednesday and Pugsley. Press on Party City's Vampiress Nails ($3) and paint a coat of Deborah Lippmann's Nail Lacquer ($18) in Ruby Red Slippers on top. You may be creepy and kooky, but you're anything but ooky.