From the hilarious tv cartoon Ren & Stimpy, happy happy joy joy
is defined as when the world expects you to put on this happy and joyful face when what you really want to do is shriek at the top of your lungs and rip your hair out in anger/frustration/misery. To make everyone happy though, you put on this mask of happy happy joy joy while singing a silly song.
Just as you were ready to leave work for the day, the boss tells you he wants you to work both Saturday and Sunday on the new project. You're on salary and so will get no more $$ for sacrificing your weekend. However, the boss is considering you for that vacant position where you'd have your own office with a window, so you happy happy joy joy
and say, "Sure thing, boss!" with a big toothy grin on your face.