Tomorrow (October 21) is Sydney's best friend's birthday. Yes, Sydney H. from her daycare class was born only 3 days earlier than our Sydney.
Sydney M. is going to give Sydney H. this little pillow with a rattle in it and a picture of the two of them. The caption says, "Sydney2, Best Friends." (In the actual caption, the 2 is a superscript. When Sydney H's dad sees the two of them playing together, he always says, "Sydney squared!" So that's where that reference came from.)