In her introductory installment, "The Wrong Man", Megan's personality was completely different although she was played both times by Jaclyn Smith.
Bob tells the crew in the diner that he was "listening though the air duct" into Becker's apartment in order to detect anything going on with Megan. However, Becker has complained constantly about how the radiators in the apartment don't work. Air ducts are part of a central heating system, which Becker's building apparently doesn't have.