Madeline and Colin are best friends and play together beautifully all day long (except for when they are fighting, which does happen). I just love it. They also have very funny conversations between the two of them. I sometimes stop what I'm doing just to eavesdrop. Here's one from today when I told them to go get dressed:
Colin: Mads! This is my room! Go get dressed in your own room!
Maddie: No! This is Ethan's room!
Colin: This is Ethan's room and my room! See...that's my bed, and that's Ethan's bed.
Maddie: Oh! Your bed and Ethan's bed! My bed is in my room. Want to come see?
Colin: Okay!
And they run off to Maddie's room.
Love it. Love them.