As an in-joke, one of the songs Norton plays on the piano is "Melancholy Serenade," the theme of The Jackie Gleason Show (1952). That is the song "from a long ways back" that Ralph puzzles over before he's interrupted by his neighbor banging on the door.
Norton does actually play the piano in this episode. Among his many other talents Art Carney was an accomplished and respected pianist.
In 1997 "TV Guide" ranked this episode #6 on its list of "100 Greatest Episodes of All Time"
Ralph's reference to the "12-year-old kid" was Gloria Lockerman, who won $16,000 on The $64, 000 Question (1955) in September 1955. Her category was "Spelling Bee," which is why Alice challenged Ralph to spell "antidisestablishmentarianism."
"The $99,000 Answer" is an allusion to The $64, 000 Question (1955), a hit game show on CBS at the time.