Continuity mistake: Dr. Melfi is in session with Dr. Elliot Kupferberg. Elliot picks up his water bottle and the popup cap is on the bottle. In the next he is drinking from the bottle, but he isn't shown removing the cap. (00:40:57)
Continuity mistake: When the FBI dude follows Tony outside to talk to him, Tony's Escalade is visible behind Tony. When they cut away to the next shot and then back at Tony, there's a red Jeep where his Escalade was. (00:08:05)
Revealing mistake: The Ukranian woman's body by the stairs keeps changing positions all the time (depending on the angle), despite her being dead.
Continuity mistake: When Tony gets into Holsten's the man with the moustache sitting in the first booth facing the entrance is wearing a ring on his right-hand middle finger that disappears when Tony is seated. (00:54:19)
Answer: That's not Jimmy, just a look-a-like. Jimmy's short and stout, the guy in "Christopher" episode is tall and medium built. The hair is also different.