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 door and window.
The Telltale Moozadell - S3-E9
Visible crew/equipment: After their school meeting about AJ, while Tony and Carmela walk outside talking about AJ's lack of punishment, as the camera moves backwards, the camera's dolly track is visible at the right side of the screen.
To Save Us All From Satan's Power - S3-E10
Visible crew/equipment: After the little boy cusses at Santa (Bobby), when both Silvio and Paulie tell the boy to go apologise to Santa, in the wide shot as the boy walks back, we can see a red T-mark taped to the floor in front of the boy's mother.
Visible crew/equipment: Paulie and Christopher convince Tony to head out and try to locate them, and to bring them food as well as shoes for Paulie. In the wide shot, just as Tony puts on his shoes and tells Gloria, "I gotta go," there's a red T-mark on the wood floor at the lower left side of the screen.
Visible crew/equipment: When Jackie and his crew get to the poker game, an actor's red tape mark (double toe box type) is visible on the floor near the poker table. This will be where Carlo Renzi stands with his shotgun.
Visible crew/equipment: When AJ tries on his new military school uniform, he's pressured to also put on the hat. Then, after AJ looks at himself in the mirror, just as he walks back toward his mother, the reflection of the boom mic becomes visible in that mirror directly over Carmela's reflection, at the right side of the screen.
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.