Beginning with the fourth season, the jazz arrangement of the series theme was replaced with a more contemporary-sounding funk arrangement. The opening montage was changed too, showing Dr. Hartley going to work, not returning home at day's end.
'The Peeper' stated he was offered $60,000 for his invention. When adjusted for inflation, that is equivalent to $290,275.00 in 2020 dollars.
This is Tom Poston's first appearance as 'the Peeper'. He'd appear in 5 more episodes throughout this series.
This episode most likely inspired George Utley in Newhart.
Tom Poston would not only play George the handyman on Newhart (an endearing male airhead character like Howard is on this series), he'd later marry Suzanne Pleshette.