Continuity mistake: When Hesh and Massive Genius are talking on the porch, Hesh is leaning forward and picks up a glass of ice tea. A second later, in the next shot he is sitting back in his chair, and is no longer holding the glass.
Continuity mistake: The scene where Hesh and Massive Genius are sitting down and drinking. Massive Genius has just requested that Hesh pay reparations money. Paulie then steps forwards, aggressively demanding "or what?" Behind him, Chris is standing by the white pillar. However, two shots and 2 seconds later, when the camera cuts back to Tony's holding Paulie back, Chris has completely disappeared from the veranda - he is neither behind Paulie or Silvio.
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.