...And the whole dang family starts laughing

We just got back from fancy dinner out, and I'm walking down the stairs to the basement, while talking to me sister and suddenly I scream a high pitched girly squeal of terror. I look again at what freaked me out and start laughing uproariously.
"I just scared myself!"
My sister walks over to see how. She looks down the stairs and shrieks. Then she starts laughing too.
Our dad comes to see what's happening, and just says, "Oh my god."
My mom calls out from across the hallway, "What's going on?"
"Come see for yourself!" My dad replies.
My mom looks down the stairs, and joins us in laughing.

What was so funny, you ask?

Well, here you go:

Lady Elisabeth