As goblins and ghosts, elves and other sprites hover in the Halloween glow and costumed forms gather in the night, don't panic if you're caught without a change of persona for your masquerade party this weekend.

Elaborate costuming is unnecessary. Ex-trick-or-treaters from Halloweens past can transform themselves into fantasy-world characters with the right makeup and a few props. You can--abracadabra-- become a:

Cat--Whiskers ($1.75), tail ($2.95).

Devil--Horns ($5), ears ($2.95), tail ($2.95).

Green Witch--Hat ($3.75), witch's nose ($1.95), warts ($1.75), black tooth wax ($1.35).

The two most popular choices for this Halloween and last: the clown and vampire. The makeup guidelines for creating these characters yourself are from Mark Chorvinsky, owner of Dream Wizards, Rockville (a fantasy specialty store which carries costumes and makeup). Chorvinsky recommends Zauder's makeup: It's less expensive, the colors are good and it's easy to apply.

Remember: When the party's over, grease paint makeup can be removed with cold cream, makeup remover, or Crisco shortening.

To Be a Clown

* Apply a foundation of Clown White to your face: Wet your fingers, scoop it out of the tin and smear it all over. It will look splotchy. Pat your face very gently all over--eyes, forehead, cheeks, chin--to distribute makeup evenly.

* Theatrical face powder--Use a brush, pouchoir (a sock filled with powder) or a cottonball to apply the powder (baby powder or talcum powder can be substituted but theatrical powder is thinnner and covers evenly). This sets the makeup.

* Liner color--Draw an outline of the mouth shape you want; using a toothpick, remove the white base. Fill in the mouth with red liner. (Start small in drawing the mouth; a clown face is most effective when understated.)

With blue liner, draw two blue circles just below the cheek bone. Put two dabs of blue in the middle of the eyelids and a little red liner under the eyes.

* For fine detail--With black makeup pencil, draw perpendicular lines below the eyes, on eyelids, on the chin and in creases at side of eyes. Option: Draw light blue eyebrows, outline mouth in red or black, pencil in stars on cheeks, or line eyes.

* Powder face again; then lightly brush off excess powder. This sets the lines and helps to keep makeup from rubbing off.

* Complete the character by adding a clip- or tie-on (red ball) clown nose ($1.95), curly wig ($18, $22), top hat ($3.95), white gloves (never bare hands), oversized -- maybe mismatched -- shoes, or special clown shoes that clip over your own (about $20).

A Vampire?

*Use a damp sponge to apply pancake makeup (or use your wet fingers to apply a very pale coating of Clown White) all over your face. Be sure to cover up to the hairline, all the way to the ears and below the neckline. Keep this application light.

* With a stick of black liner, dab the black in a line just below the cheek bone. The shading is done by blending the black gradually--bringing the line down--until it appears gray, for a gaunt, ashen look.

* Draw eyebrows with broad strokes using the black liner: Extend the eyebrows further down toward the nose, then up in the middle of the brow at the arch and up again at the end of the eyebrows. Fill in detail with black makeup pencil.

* Dab black liner under both eyes and on top of eyelids. Blend and smooth it in. Draw pencil lines around the side of the nose and down alongside the mouth; shade it in with fingers. Draw lines on the inside of the eyes. (Hypnotic eyes, remember, are essential for this creature.)

* Blacken lips with black liner stick. Apply stage blood to corners of the mouth, letting it trickle down the chin.

* Fangs: A pair of inexpensive white plastic fangs ($1.50) cut in half will do the job, although they may be uncomfortable. The new Fang Form Kit ($5) provides material to make your own, and dental adhesive to attach them. They look horribly authentic and you can save them for next year's prowls.

* Widow's peak: Comb hair back, draw a triangular widow's peak with liner and pencil. To gray the hair, apply liquid mascara (it shampoos out).

Throw on a cape, stand back and wait for the blood-curdling screams to begin.

To put together your own Halloween makeup kit, check with stores listed under Theatrical Makeup in the Yellow Pages.