Keep Circulating the Tapes: Season 2 specifically. Odds are you can still find a Region 1 DVD set, but it's noticeably costlier than the more readily available Season 1.
Missing Episode: Eight episodes from season 2 were unaired due to the show being prematurely canceled, though they are available on DVD.
No Export for You: Season 1's DVD set was released pretty much everywhere the show was aired. The DVD set for Season 2 was only ever released in Canada, while they will play on most Region 1 DVD players, they're long out of print, not to mention very pricey.
The Other Darrin: Gina was originally played by a different actress on a 1997 episode of Friends.
Screwed by the Network: NBC made the boneheaded decision to put Joey opposite American Idol and predictably its ratings soon declined—to the point that the show then got canceled midway through season 2, leaving eight episodes unaired.
Added bonus. As the trope header says, Kevin Bright had none to kind an opinion of NBC reconstructing the Joey character, coming out and blaming them for the show's failure on more than one occasion.