According to Jim: The Baby Monitor

Cheryl wants to become friends with a new couple, Ted and Janet, who've moved to their street, but worries they'll be put off the family once they've spoken to the rest of their neighbours. She lends Janet a baby monitor and soon after the new couple have dinner with Jim and Cheryl. Things go really well until Cheryl finds that they can pick up Ted and Janet's bedroom conversations via the other baby monitor which is at their house, and Jim puts his foot in it by mentioning the nickname that Ted gives his genitalia in a conversation