There are some really cool examples that use white balloons for owls, filled with helium, clutching a scroll invitation. Due to expense and hassle, we decided to forgo the helium and attach the owls directly to the scroll.
Here's sample invitation text to place on parchment paper (the logo background won't show up as white when you actually print it):
Blow up the balloons, grab a Sharpie to create your owl, and attach the scroll invitation to the owl "feet" (the tied part of the balloon) with the twine.
The fun part is the hand delivery! The recipients LOVE having the invitation specially personalized just for them.