I always get a kick out of noticing the random set dressing on old sitcoms, be it the inappropriate for the character band posters on a teenager's wall, the protagonist's VHS collection, cereal boxes with the logos blacked out or books lining the shelves. I have been rewatching Cheers starting with the first season on Netflix Instant, and amongst the classic Boston sports ephemera lining every square inch of the bar's wallspace is a poster for future Hall of Famer Dennis Eckersley. While Eckersley had a solid career as a starter for the Red Sox, and had been with the team for five years in 1982 when Cheers debuted, including one 20 win effort, he was nowhere near the superstar he would be when he became the dominant closer for the late 80's-early 90's Oakland Athletics.
Seinfeld is another goldmine in this regard, for example if you pay close attention at any episode where the quartet goes to the movies you will notice this poster for the long forgotten 1992 Tim Daly/Penolope Ann Miller comedy Year of the Comet, which shares Seinfeld's production company, Castle Rock Entertainment.
Recently, while watching the 14th episode of season three, The Pez Dispenser, I noticed none other than Carl Gottleib's journal of the making of Steven Spielberg's Jaws, The Jaws Log, on Jerry's bookshelf. I wrote briefly about the Jaws Log a few years ago, which you can check out here.
There it is on the second shelf, two books up from James Clavell's Shogun. Somebody might want to inform Jerry that a good conditioned copy of that edition is going for $35 on eBay.