Other mistake: In the scene where Paulie Gualtieri goes to confront "Feech" La Manna at the bakery concerning the landscaping feud, the clock on the wall doesn't match the time on La Manna's watch or the clock on the wall behind La Manna's desk. The big clock says 11:55 while the other two say either 2:45 or 9:10.
Revealing mistake: After Tony's unsuccessful meeting with Johnny due to Christopher's inability to keep his mouth shut, while Tony and Chris are driving past stores, we can see the reflections of the filming equipment attached to the roof of their vehicle.
Visible crew/equipment: When Tony and Pontecorvo pull up to the clubhouse in the golf cart, as Tony walks toward the neurologist, there's a red T-mark on the ground at the bottom left corner of the screen.
Answer: Yup, just like Nicholas Lea was chosen to play Alex Krycek on the X-files after showing up on 1 episode as a different character.
Grumpy Scot