The shocking secret behind the JOLIE-PITT twins’ anxiety at the appearance of beardless Brad.

 "Where’s OUR daddy?!"

That’s what Brad Pitt and Angelina Jolie’s confused twins were left wondering after Brad, 46, shaved his scraggly beard!

The A-listers’ youngest  – 2-year-old Knox and Vivienne – were so accustomed to Brad’s untamed facial hair that they barely recognized him when he got smooth for his new film Moneyball.

"Brad kissed and hugged them when he left for the hairstylist.  But when he came home three hours later with his hair cut, the gray dyed out and his face totally smooth, Knox and Vivienne ran away from him screaming.

"They ran up to Angie, practically in tears, begging, ‘Where’s daddy? Who’s THAT man?’"

Angie, 35, had to explain that the newly-shorn man was their father, said the source.

"Knox and Vivienne were so young when Brad started growing his beard that they didn’t know him any other way," the source added.