Sheldon goes to the model train store to hear a lecture on model trains, and is convinced into buying an HO gauge model train set. Teleplay byвЂЉ: Bill Prady & Steven Molaro & Dave Goetsch Story byвЂЉ: Chuck Lorre & Eric Kaplan & Jim Reynolds Title reference: Sheldon worrying over what hazards Penny's chair might contain. Note: Melissa Rauch is absent in this episode. He constantly pesters Penny to dispose of it, to no avail. Penny gets a new chair, which Sheldon enjoys until he finds out that she picked it up from the street. Teleplay byвЂЉ: Chuck Lorre & Jim Reynolds & Steve Holland Story byвЂЉ: Bill Prady & Steven Molaro & Maria Ferrari Amy also reminds her that, she still is considered 'great'. Title reference: Amy has a term for Penny's behavior that is responsible. Penny feels that this has damaged her relationship with the guys permanently and decides to move back, as she has not had any worthwhile acting jobs since moving. Raj has feelings for Penny and talks to her about the recent events. Raj finds himself in hot water with Leonard after his night with Penny and also with Howard. Teleplay byвЂЉ: Chuck Lorre & Bill Prady & Steven Molaro Story byвЂЉ: Eric Kaplan & Maria Ferrari & Anthony Del Broccolo ( November 2016) ( Learn how and when to remove this template message) Please help improve them by removing unnecessary details and making them more concise. This section's plot summaries may be too long or excessively detailed. The Soyuz capsule was constructed based on photos from NASA, the Kansas Cosmosphere for dimensions, and scavenged parts from an aerospace junkyard in Los Angeles. Thanks to technical consulting from astronaut Mike Massimino, who also plays himself on the show, the production crew was able to put together sets that realistically depicts the Soyuz capsule and the ISS. The season finale depicts Howard Wolowitz traveling to the International Space Station (ISS) on board a Soyuz rocket. Mike Massimino later appeared in the season 6 episodes ' The Decoupling Fluctuation' and ' The Re-Entry Minimization'. Stephen Hawking went on to appear in the season 6 episode ' The Extract Obliteration' and the season 7 episode ' The Relationship Diremption'. Astronaut Mike Massimino appears in ' The Friendship Contraction' and ' The Countdown Reflection'. In the following episode, ' The Hawking Excitation', cosmologist Stephen Hawking appears as a guest star. In ' The Transporter Malfunction', actor Leonard Nimoy appears as a voice actor, playing an action-figure Spock that Sheldon imagines talking to him. Several high-profile celebrities appear in the season. Robert Clotworthy as Dave Roeger (voice).Lynn Phillip Seibel as Professor Rothman.

The big bang theory season 2 episode 1