There are some costumes that should not worn at little kids birthday parties. Santa, magicians, comic book heroes, they're fine; however, Darth Vader is not one of them, especially by surprise.
Imagine this. Someone unexperienced dressed like Darth Vader. He hides behind the curtain, waiting to be called. The unexperienced Darth Vader is pumped up, so in the middle of the happy birthday song, it goes like this.
Party: Happy Birthday to you-"
*opens curtain*
Darth Vader: HAPPY BIRTHDAY JEDI!
Now, the kid doesn't go, "Yay! Darth Vader is here!" No, no, no... He looks at him, then to his mom, in panic saying, "WHO THE F*** BROUGHT DARTH VADER HERE???!!!!" So he runs across the other side of the room.
Darth Vader wanted to help him, so he extends his arm toward him. If you don't remember the force choke, you never truly watched Star Wars. He extends a hand. The kid watched Star Wars, so instinctively, he grabbed his neck. Darth Vader was panicking on what to do.
Just then, a clown came in to cheer him up. "Don't worry kids! It's just Darth Vader!" Now there are two things that scare kids the most: Darth Vader & Clowns, and they're working together. You imagine what happens next.
