: The episode ends on a rare moment of connection between Dick and Mary when they both realize they are 42 years old (though John Lithgow and Jane Curtin were both older in reality). Production Trivia
: Dick becomes offended when Mary Albright gives him a teasing birthday card mentioning he looks "old and wrinkled". His insecurity is compounded by his attraction to a young anthropology student, Laurie, played by guest star Lauren Graham in one of her early roles.
: Jane Curtin’s laughter during the leather pants scene was genuine. The producers used an outtake for the final cut because her reaction was so authentic.
: Desperate to feel young, Dick dyes his hair jet-black and squeezes into incredibly tight, squeaky leather trousers—a look that has since become one of the series' most iconic visual gags. Themes & Analysis
"3rd Rock from the Sun" Dick's First Birthday (TV Episode 1996) - Trivia - IMDb