Robin Roberts I Got Bad Habits From My Sister's Bone Marrow Transplant

4/24/2014 12:30 AM PDT

Robin Roberts picked up some unexpected side-effects -- good and bad -- when she got a life-saving bone marrow transplant 2 years ago ... and says it's all her sister's fault. 

Robin's sis Sally-Ann donated the bone marrow to help Robin treat a rare blood disorder.

The transplant gave Robin a fresh infusion of stem cells ... but Wednesday in NYC -- she told us she also inherited some of her sister's physical traits.

Watch Robin's explanation -- doesn't sound like she's too upset about the trade-off ... as long as she's not around chocolate.