Show up at party nr 1, then after 5 minutes get to part nr2. Then continue to shuttle between the two parties like that for an hour, excusing yourself to the guests saying you need to use the bathroom. This way people will think that you are attending both parties. (They may also think you have a bad stomach as you run off to the bathroom for the 15th time, not knowing you are sneaking out to the other party.)
Hey, it worked on TV!
Thom@s (What are you all looking at me like that for?
"If guns don't kill people, people kill people - does that mean toasters don't toast toast, toast toast toast?"