How to Make a Surprise No More?

I picked up a cake for Daddy's birthday and told Sienna to keep quiet about it. She was very happy to cooperate. We were both expecting how pleasantly Daddy would be surprised. Then I had a little fight with her about something that she wanted and I didn't want to bend on giving. I don't remember what. She started doing "I don't like you, I like Daddy" routine, which didn't work as usual. Then she surprised me by saying, "Now I am going to tell Daddy about the cake. It's not gonna to be a surprise any more." She still didn't get what she wanted. But she sure could be naughty, uh?

I like it when Sienna gets naughty. First of all she doesn't get naughty very often. Secondly, when she does, her smartness shines through just like when she is well-behaved.