In the scene where Frost and Jane leave to go to the dance studio from the police station, the color of Frost's shirt changes from blue to white and the tie changes also.
Looking at a dead body, Dr Isles says, "Penetrating stab wound between the third and fourth intercostal." "Intercostal" means the space between ribs, so between the third and fourth intercostal, there's a rib. Since the victim was stabbed with a pair of scissors, it's possible she meant stabbed through both the third and fourth intercostal.
Jane Rizzoli mentioned that she learned ballet with Mrs. Peabody. She pronounced it as "PEE-BAH-dy". However, the correct pronunciation is "PEE-bud-dy ". Rizzoli is native Bostonian. She should have known that.