For invitations, I made 3D space shuttle replicas with an overhead hatch from which Gabby's image could be pulled out. Upon doing so, her tube (the one that attaches the astronaut to the shuttle when they do repairs on space stations) showed details of the party: "blast off with me for my 3rd birthday at... on...etc.)
For the party itself we prepared astro-pack backpacks. I bought 4-bottle wine boxes from papermart.com and decorated them with a space logo and details of the party. Then I bought tote bag strap material from Joann craft store and attached these to the back of the wine boxes to create a box-backpack. Contents of the lootbags included space putty (which I made myself from an online recipe), a UFO (flying disk), Alien inflatable from ustoy.com, among others. I relied heavily on orientaltrading.com, ustoy.com and windycitynovelties.com for my lootbag contents and for party prizes.
We decorated the venue with space-themed balloons which I designed and created myself. There was a huge balloon astronaut, mini-astronauts and mini-alien centerpieces. I bought "agate" balloons from bulkballoons.com and inserted a balloon light (windycitynovelties.com) in them prior to inflating and the "planets" on the centerpieces lit up during the party. Overhead we inflated red and blue 11" balloons and silver, red and blue 260Q twisty balloons and hung them on beams located throughout the venue. For giveaways we inflated silver 11" round balloons and wrapped them in inflated red or blue 260Q twisty balloons to simulate Saturn. We also hung inflatable space shuttles and aliens all over the party place. For the backdrop of the stage I bought a blue corrugated board with white stars on it from Shindigz.com. On the backdrop I taped silver cutouts of the letters of Gabby's name.
On the day of the party, Gabby dressed up as an astronaut complete with a helmet and inflatable space shuttle ride-on. During the party we had 2 activity tables: the photo booth and the space beads booth. For the photo booth we prepared big boards with paintings of a faceless alien, a faceless astronaut and a space ship with a hole. Kids took turns posing in these photo cutouts while we took Polaroids of them to bring home in a space themed picture frame (obtained from orientaltrading.com). For the space beads, kids made their own bracelets or necklaces out of space-themed foam beads and alphabet foam beads (so they could spell their names). They got to take home their creations.
This party was 3 months in the making and things got pretty hectic around 3 days before the party. But it was worth it. To this day, my friends and relatives still rave about how unique and special that birthday party was!