Ladies and Gents: A birthday card for a 23 year old co-worker?

He's more of an acquaintance and very fun to talk too! We are both cashiers and we've developed a great friendship :) Also, I kinda sort of didn't get the memo on his birthday (so this card will be belated...) Any ideas as to what I should write in it, please...some thoughtful suggestions would be awesome and greatly appreciated....thank you in advance.