Continuity mistake: In the scene where Bacala is telling Uncle Jun about his father and the accident, Uncle Junior gets angry and starts throwing things around, he is wearing glasses. You can see that in between throwing one of the items, he is not wearing his glasses, then he is wearing them again.
Visible crew/equipment: After Tony gets written up for speeding, it then cuts to Bryan Spatafore parking his pickup at the curb, and just as the pickup's door opens and closes, we can see the reflection of the boom mic on the vehicle's window.
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.