"Surprise! I sent you these gifts! It may not be a lot, but I spent a long time picking these out for you! I sent it a few days before you changed addresses, I hope it gets redirected to you..."
(Assuming between close friends)
짠! 이 선물들 보냈어! 대단한 건 아니지만 네게 주려고 한참 동안 공들여 직접 고른 거야! 주소 바뀌기 며칠 전에 보냈는데 새 주소로 보내져야 할 텐데...
* "짠!" for "Surprise!" is mostly used in face-to-face situation like a sound effect. You might use it if you and your friend are very close and often playful with each other. Otherwise, you might use 몰랐지!?(You had no idea, did you?) or 예상 못 했지? (You didn't expect it, did you?).