Subject: Top Secret Mission: [Brother/Sister]'s Birthday Bash!
Hey [Friend's Name],
Get ready for some serious fun and planning! It's time to throw an epic surprise birthday party for [Brother/Sister]. I'm so excited, but I need your help to pull this off without them catching wind of anything.
I'm thinking [location] for the party, and we can do it on [date]. What do you think? We could have [theme or idea for the party]. I know [he/she] loves [hobby or interest], so we could incorporate that somehow.
I'm also thinking about [food and drinks]. What do you suggest? And we definitely need some awesome decorations and music to set the mood.
Your input is super important, so let's brainstorm and come up with a killer plan. We can meet up [time] on [day] to discuss everything in detail.
Remember, this is top secret! Let's make this birthday unforgettable for [Brother/Sister].
Can't wait to hear your thoughts!
Best,
[Your Name]