"Dad Box Birthday Song" is a song unnamed in the show that plays at the beginning of "Birthday." Bee's Dad Box sing's her a birthday song in her dad's voice.
Lyrics
Don't be sad, I'm still your dad
I'd be there if I could
I sure hope that you're not broke
and everything's been running good
I'll always be in your memory
but today I just want to say
Way to go at keepin' on going
Have a happy birthday