I posed the question back in this post that if there are supposed to be 13 episodes of Jack's Big Music Show, where are the last two? Fortunately two readers have come to the rescue and got the straight dope about what's going on in the clubhouse. First, Bill from TVforTots.com contacted some people he knows at Noggin/Nick, who told him that a new episode "King of Swing" featuring musician Buddy Guy will air on February 6th.
Then MDD reader Andrew contacted Spiffy Pictures (producers of JBMS) who told him that the 12th episode will indeed be in February, the 13th will be in April, and another 13 episodes will air in the fall. He also asked about merchandise, and was told that there will be Jack-related items in the stores before next Christmas.
So big thanks to Andrew and Bill for getting the answers (and making the phone calls I should have made). [Insert "you sure are swell" comment here.]