When the whole world falls under the spell of Christmas, it generally stays in the house, keeping warm and wondering vaguely what to do after the presents are unwrapped. Should we light a fire in the fireplace? Does anyone recall how to make colors in the flames? Do we figure out next year's Christmas card list? Who bought marshmallows? Anyone for "Authors"? Who'll be first to read aloud from "A Child's Christmas in Wales"?

Had enough of Christmas? After all, there are other things going on: Christmas this year is a Saturday night and a few places remain open, to remind us that there is life after the holidays.

Movies on Christmas are a tried-and-true pastime: Reports differ as to whether nobody's there or everybody's there. But one person who will be there is PETER PAN, as the Disney classic is re-released on Christmas in area theaters.

It seems the museums are closed for the day, but they can't close the LINCOLN and JEFFERSON MEMORIALS. A little windy, but why not?

The man who added to the fame of December 25 by choosing that day to cross the Delaware continues to enhance the occasion. MOUNT VERNON is open 9 to 4, decorated for the season as it must've been when George Washington lived there -- a few modest boughs; no tree, of course. You might even forget what day it is.

If you've been promenading along the C&O canal in order to rouse an appetite before returning to the house for goose, and pass by the OLD ANGLER'S INN, and notice the glow of firelight inside, don't doubt your senses: The inn is open and serving Irish coffee and hot cider with rum in front of the fire, till midnight.

Speaking of Christmas geese, 35,000 Canadas are still flocking together at the BLACKWATER WILDLIFE REFUGE, 10 miles south of Cambridge, Maryland. (That's down from a November migration high of 65,000.) The visitors' center will be closed for the holiday, but the wildlife drive remains open during daylight hours. The four-mile drive is the best place to see waterfowl in the refuge; visitors are asked to stay in cars on the drive so those behind them have something to see: Wildlife is less afraid of cars than of people. There are walking trails, too. Look also for ducks, white- tailed and sika deer, delmarva fox squirrels and possibly bald eagles. (Phone: 301/228-2677.)

Want to get your fingers measured for your new BOWLING ball? Brunswick River Bowl in Bethesda joins many other local lanes in being open on Christmas. Their hours will be 2 to 11, and Bowl America Shirley on Edsal Road in Alexandria will be open from noon to 10 or later, depending on business.

New skates? Try the ICE RINK in Pershing Park (15th and Pennsylvania NW), from 11 to 9, or the Sculpture Garden rink, 11 to 11:30. Rollerskaters: Congressional ROLLER RINK at the south end of Congressional Plaza on Rockville Pike will hold a single session Christmas night, 8 to 10:30.

There's more to Christmas night than carols: There's basketball. The BULLETS play Atlanta at Capital Centre, starting at 8:05.

It means, NIGHT SKIING, too, at Ski Liberty in Fairfield, Pennsylvania. They're skiing on Christmas from noon until 10. (Phone: 717/642-8282.)

Instead of listening for jinglebells, you could be dancing. Waking up at 7:30 p.m. and staying that way until 3, is THE BAYOU (3135 K Street NW), where The Process, a local rock band, will be appearing. At DEJA VU (2119 M Street NW), which opens at 8, the disc jockey will be playing music from the '50s and '60s, as usual. Doors open at the WAX MUSEUM (Fourth & E streets SW) at 8:30; the R&B jam of Bob Margolin's Band starts at 9. Admission is $2.50, but free if you bring your own harmonica.

Maybe there's one in your stocking.