Yes, that's Barbara all snug as a bug inside a casket -- her idea of a surprise for her friends and family members who had shown up to celebrate her 70th birthday last weekend. Once the shock wore off ... it looks like everyone was in on the creepy and totally morbid bash thrown in Manhattan.

Her fellow Sharks, including Mark Cuban and Daymond John and Robert Herjavec, gathered around her casket to pay their respects. Daymond even gave her a kiss!

Barbara eventually popped up to join the party ... in a Carolina Herrera gown no less. Think "Finnegans Wake" (look it up) -- she IS part Irish, after all.

As funerals have often been described as the best party you don't get to attend, BC decided to design a workaround. As she put it, "What the heck, you only die once, you might as well be around for it!"

Okay, we admit it ... we're dying to see what she does for 71.