You thought they all forgot but then opened the door and HAPPY BIRTHDAY

He had no point of reference though so he was probably all like WHAT IS HAPPENING 

Want more Happy Birthday Memes?

• Happy Birthday Memes to Share With Friends and Enemies
• Animal Themed Happy Birthday memes
• All the Birthday Memes on Know Your Meme

Those ought to keep you busy for a while. If not, this Google image search of all the top happy birthday memes might help even further. It is your friend's birthday and then deserve to laugh on their special day, or at least breath heavier out their nose for a few seconds.