When you are going to surprise someone, expect a backlash. It isn’t always going to come out the way you wanted. You might catch someone in the middle of a mess and seeing you, doesn’t solve any problems. Remember the reason why you are doing the surprise and that the recipient does not expect you.
A friend of mine tried to surprise me at work, but he came at a bad time of total chaos. He meant well but didn’t get the reaction he expected. Although I have told him many times that surprises are a bad idea, he still tries and it goes terribly wrong. When I gave my apologies after work, he was so steamed about my reaction that he didn’t even acknowledge that an apology was made.
In my opinion, surprises don’t work. If I had known he was coming beforehand, I would have asked him to come later so he would have missed the chaos and get me in a better mood.