When JD is holding the hand of the girl in the MRI, she says she isn't checking for a wedding ring while stroking his ring finger. She is holding his right hands, and a wedding ring would be on his left hand.
When J.D. is in the MRI room, the MRI is supposedly on, but it's not making any noise at all, and he's still wearing his pager, stethoscope, watch, etc. In actual fact, a doctor would not take any metal objects into a room with an MRI scanner.
When Elliot is shown with a baseball catcher's equipment on, she is wearing a left handed glove. (The glove is on her right hand, meaning she would throw left handed.) In baseball, a catcher is always right handed, because most hitters are right handed, so a right handed catcher has better command of the diamond.