Hey, It's That Voice!: No kidding on this one, since the '80's series got the best voice actors in several animated shows in the 80's/90's while both the 2000 specials and Adventures in Care-A-Lot got The Ocean Group backing them up. Resulting in:
No one would believe that Friend Bear is actually Jean Gray.
Ai CAL, being back in the hands of DiC, brought in VAs from DiC's regular casting agency, Ocean Group, who were also providing casting for the My Little Pony series since My Little Pony Tales, and most recently for My Little Pony Friendship Is Magic. Makes you wonder if these ponies can use their cutie marks to stare out of their rump... Hence, in hindsight, we got:
The Other Darrin: Sort of. Billie Mae Richards, the voice of Tender Heart Bear in the first two films and the DIC TV series, and Jim Henshaw, the voice of Bright Heart Raccoon in the first two films, had their roles switched in the Nelvana TV series.
The Latin American Spanish versions does this to ridiculous levels, because not only they switched out voice actors, they also switched voice acting studios and even studios from different countries. Just to give an idea, here is the whole story: The movies (with the exception of the Nutcracker Suite special) and the DiC TV series were dubbed in Mexico (and each movie were dubbed with different voice actors, with the only exception of Tender Heart Bear's VA), the first half of the Nelvana TV series were dubbed in Chile and the second half (when Shreeky appears for first time) was dubbed in Venezuela and the most recent specials and TV series are dubbed in Argentina right now.
Since the TV specials, many characters went through this. See here for voice history.
No Export for You: Oddly enough, Japan only got the second movie (A New Generation) of the original movie trilogy and none of the animated series until the 2000's direct-to-video specials. Taking into account the Japanese (and mostly East Asian) taste for anything cute and cuddly, it's really odd that the franchise skipped those audiences for many years.