Cyril Fletcher jokes that the answer to a blank ending in "Mouse" should be "Quatermouse". However, the reference is to the Quatermass character overall, and not related to any specific film or TV series.
Alison comments, "I wish Bernard was here", only to be told that "British Rocket Group's got its own problems" - Bernard being Bernard Quatermass, head of British Rocket Group in the TV series bearing his name.