It can often be hard to come up with appropriate invitations for a twin birthday party. This is a cleaver idea to incorporate twins without screaming TWINS. The invitation is one of the preprinted and you fill in the invitation but I thought it was very cute and it can lend itself to lots of directions in a theme.
This particular party was for two very active kids and was at a Pump It Up facility. It was a perfect 6th birthday party idea.
Resources: Invitation found at Paper Source.