I accidentally found out my sister is planning a surprise birthday party for me...what do I do?

[Brit]

I'm turning 18 in February, and I accidentally discovered that my little sister is planning a surprise birthday party for me in January when I went on facebook and it was still logged onto her account. What do I do? How do I act surprised on the day of my party? I don't want to spoil this for my sister.

[...◊³]

wow
your nice..

[THIS IS MADN3SS]

Wear a mask

[Kelly]

Just don't have like a bored expression.. when my friends surprised me I wasn't like WOOWW! I just stood there and stared at everyone.. then I was like thanks everybody!
Just be really happy

[jbluvr4evr44]

distract yourself .........?

[Spooky1]

Just practice your surprised face! and hope it works.

[boo boo]

act suprized lol thats so nice of her

[Angie]

When The Day Comes Just Smile Real Big. && Hug Everyone. Because People Don't Expect You To Be Surprised At Your Party They Expect You To Be Grateful. So Just Give Thanks 2 Your Sis. And Smile, Hug, Laugh. And Happy birthday

[Christine]

You don't have to be a Hollywood actress to pull this off. Just pretend to be surprised. Do NOT let her know that you found out. Even if it's hard to pretend, give it everything you can and do it for her.

[Mandy]

be a dick! when you know you are supposed to arrive at the place, dont! tell her you can't go to wherever she wants you to. play difficult!