I haven't seen the ninjas in many years, but I could swear that when they first came out they DID have little shells on their backs.
Just watched the vid without sound....it's obvious, these are NOT the real ninjas!!!
You're just going to have to tell your nephew or niece that these guys are imposters! Here's a pic of the REAL ninjas, and it's obvious that they DO have shells. And a turtle CANNOT come out of its shell, as we all know. IMPOSTERS!!!