Russell Hornsby injured his leg (Achilles tendon) prior to shooting this episode and was written out as being "on vacation". He didn't return until 'Kiss of the Muse' two episodes later. This was the reason for wheeling him off set in his office chair.
Nick references a temperature of "346 degrees below zero." This almost certainly indicates that he means "Fahrenheit," which converts to approximately 63 Kelvins. A temperature of "346 degrees Celsius below zero" would result in -73 Kelvins, which is 1) an impossible temperature (unless created under laboratory conditions and 2) not colder than 0 Kelvins, but actually hotter.