Audio problem: When Tony confronts Carmela in the backyard about the pool having been drained, when the shot changes to a camera angle inside the empty pool and Tony says "I thought we were getting along better lately", his lips don't match his lines. (00:15:49)
Continuity mistake: At Uncle Pat's farm, when Tony sits down to breakfast and the conversation turns to terrorism, when Pat says, "Not my problem much longer," we see the newspaper in Tony B's hands in the wide shot, but it cuts to a close-up and the newspaper is turned the opposite way, with no images and different body text.
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.