Sammi "Sweetheart" Giancola won't be on the "Jersey Shore" reunion, at least not in the flesh, but the crew won't be a woman down since she's being replaced by a sex doll.

Doug Weldon is the owner of and tells TMZ that someone from production approached him in early January about making a replica of Sammi for the reunion since she wouldn't be returning. 

Sammi, who dated Ronnie Ortiz-Magro during the original six-season run of the show, said she opted out because she's in a different place in her life than she was during the first run of the show. 

Enter Doug, who says he was told the doll would be a huge part of the show, but making a carbon copy of Sammi's face was a no-go since it would've taken 6 weeks, and there wasn't enough time before filming started.

Production bought a standard 5' 5'' doll from the website that Doug reduced to C cups. He also provided them with two female heads and made them look like Sammi ... using the right shade of makeup along with 4 wigs, so production could match her hairstyle. Total cost ... $1,840.

Doug says he shipped the goods to Miami in a box that the crew can be seen opening in the trailer. We're told it makes its official debut in the first episode. 

Snooki's reaction is priceless ...