With Charlie, I always had plenty of extra clothes for him at the babysitter's house. Actually, there was a blue basket with his name spelled out in stickers.
With Alice, there's a crinkly plastic grocery bag with one sock, a size 6 - 9 months onesie and an old blue bib of Charlie's. Poor second baby.
I picked her up from the babysitter's a few weeks ago looking like this. Marina gave me a disapproving look and said "She is completely out of extra clothes and peed through her pants. She is wearing Charlie's shirt and underwear. Please change her when you get home." (She added that last little dig because she was pretty sure I'd let Alice run around all night wearing this. And she was right.)