My daughter plans her birthday theme months in advance, allowing plenty of time to prepare:  this year it was Harry Potter.  I made Hogwarts style invitations using a downloaded Wizards Handwriting Font, on parchment style cards. For Hogwarts decorations I got brown paper dropcloths  they come in 9 by 12 ft sheets and sponged stone bricks with beige paint left over from a house project. I sponged a bit of darker brown and white onto the stones to make them look real.  We hung these sheets up in the main living room.  I printed signs for all the Hogwarts areas: Transfiguration, Potions, Owlery, etc., using a downloaded Lumos font. On the bathroom door was a sign Beware of Mountain Trolls. My daughter drew a green-faced troll which we stuck behind the mirror, so if you were at the sink and looked up, you would see it. We purchased a Hogwarts banner and hung it in front. Outside, we set up a Playhut and place stuffed animals (dragons, unicorns, frogs, snakes) in front of it for Hagrid's Hut and Care of Magical Creatures area. We borrowed an owl puppet from the library, and hung it from our mailbox for the Owlery.  The funniest sight was a toy car, the kind you sit in and push with your feet Flintstone style, hung in a tree in the front yard for the Weasley's car caught in the Whomping Willow! When the kids arrived, my husband, dressed up with a black beard as Hagrid, greeted them and took them to a room marked Diagon Alley.  All the signs for Diagon Alley were printed in the Harry Potter font.  First they had to get a pouch (wholesale jewelry pouches ordered online) of gold Galleons (play money) from a vault at Gringotts Bank.  The vault was a shoebox with a hinged lid painted black hung up in a closet. Then they had to pick up a cauldron (a handled black gift bag) at the Apothecary, a spellbook at Flourish & Blotts (made and printed on computer), and a wand at Ollivanders (chopsticks stained with dark wood stain).  They could decorate wands by dipping the tips in glue and then in gold glitter (the Lumos spell).  Next was Madame Malkins for a wizards robe (black fabric with tiestrings attached).  On to the Common Room for the Sorting Ceremony, where a brown paper bag shaped into the Sorting Hat was placed on each child's head. We used a baby monitor to announce the hat's decision. House Crests were laminated and glued to pin backs so the kids could wear them. Each House rotated through 3 classes. In Transfiguration they did a craft  changing a lollipop into a spider, with black pom poms, chenille stems, and wiggly eyes.  A neighbor mom helped out in Herbology, where they sprinkled Flesh Eating Slug Repellent (baby powder containers labeled accordingly) on our flower garden, dug for Mandrake roots (small gingerroot pieces with funny faces drawn with black marker) in a bin of potting soil, planted pumpkin seeds with Dragon Dung Compost and taste-tested gillyweed (seaweed used for sushi).  They put headphones on to protect their ears before digging for the roots. In Potions, they poured gillywater (vinegar) into a clear cup, stirred with a black plastic spoon.  The spoons had a hidden drop of dried food coloring on them so when they put them in the water, it magically changed color! They added a scoop of powdered bicorn horn (baking soda), watched it fizz up, then added essence of murtlap (white glue solution), crushed dragon scales (glitter), and tears of phoenix (borax solution).  This made a colored goo which we called flobberworm mucus. I had small cups with lids so they could keep their potions. After the House rotations, everyone went outside to practice Quidditch. They threw Bludgers (water balloons) at Hagrid, who tried to bat them away with a small bat. Of course, Hagrid took a few hits from the balloons. Then each student was given a Marauders Map printed on tea-stained paper, for a Dragon Egg Hunt.  To get the map to work, they had to say I solemnly swear that I am up to no good. They had to find clues first Follow the Spiders, Visit the Whomping Willow, Go to the Forbidden Forest. These were printed on signs they could see as they visited each area. Plastic Easter eggs spray-painted gold were hidden in Forbidden Forest (an area outside).  Inside each egg was a small capsule which grows into a sponge creature when placed in warm water. Back to the back patio for the feast.  Tables were set with purple covers, gold moon and star confetti, gold plates, cutlery, napkins and goblets.  Plastic wine goblets from a party store were spray painted gold only on the bases, so drinking from them would be safe. Before eating they toasted Hogwarts and my daughter for her birthday.  Food was on silver platters or trays. There were white Christmas lights, gold spirals and stars hanging from the patio cover, and music from the Harry Potter movies playing from a boombox. I recorded the closing credit music from each movie and burned a CD.  Food was pizza, fruit, veggie platter, and a Harry Potter cake from our grocery.  I also made pumpkin pasties (mini-pumpkin pies). Everyone had to say Lumos to help light the candles. Before departing, each child visited Honeydukes to pick up some Bertie Botts Every Flavor Beans (Jelly Bellies prepacked and labeled in small zip bags), Droobles Best Blowing Gum (bubble gum), Ton-Tongue Toffees (caramels), and Chocolate Frogs (made using candy mold). The chocolate frogs had a pentagon-shaped Dumbledore wizard trading card attached (also computer generated), just like the movie.  By party's end, each child had a cauldron, pouch with Galleons, wand, robe, spellbook, House crest pin, spider lollipop, mandrake root, potion cup, Marauders map, gold dragon egg, and Honeydukes candy to take home. The kids had so much fun that they kept coming back to our house the rest of the week to play Harry Potter.