"It's a shame that we'll never know
The conclusion to our favourite shows
We will never know the outcome
Of those fanciful lives on TV..."
--Asthmaboy, "Down to the Puget Sound"
In no particular order, the top five shows I'd travel back in time to prolong if Hollywood were my oyster:

1. Freaks and Geeks (1999 - 2000)
This now-legendary period piece created by Paul Feig and Judd Apatow is a punch-you-in-the-gut realistic look at high schoolers on the fringe. It may be
set in 1980s Michigan, but the show itself feels universal. My personal favorite characters are the perennially hopeful-yet-dopey Nick Andopolis (mostly thanks to Jason Segel's absolute fearlessness in creating cringeworthy comedic moments); sweet, unguarded Sam Weir, who despite his lack of social confidence is a natural leader among his friends; and above all, perhaps the most heartbreakingly realistic geek ever seen on television, Bill Haverchuck. Ever since I first saw the show I've followed the careers of its stars, and I cheer as if for an old friend or family member every time a Freaks and Geeks alum pops up on television or the big screen.
2. Undeclared (2001 - 2002)
Another failed Apatow production, this half-hour comedy lasted less than a season. I was one of very few people who happened to catch the show as it aired, and it actually led me to watch
Freaks and Geeks on DVD later on. I
was in college at the time, and what drew me in as a fan of
Undeclared was
the realism. Seth Rogen, a star and writer of the show, got all the details right, from Jay Baruchel's Snood tee-shirt to the awkwardness of being sexiled by a roommate. This was no musty middle-aged interpretation of life for my generation.