A little known fact is that Radical Dreamers is the actual sequel to Chrono
Trigger, not Chrono Cross as many believe. At least in terms of release dates.
Radical Dreamers came out on the Super Famicom (Japanese SNES), but never
made it over to the States. While Chrono Cross does take up after Chrono
Trigger, there is some plot interaction and development] that occurs in Radical
Dreamers. Some of this has been incorporated into the rerelease of Chrono
Trigger for the psx in Japan, by adding new endings that explain, or at
least hint at some of the developments that will be taken up again in Chrono
Cross. Squaresoft actually gives a shout out to Radical Dreamers in Chrono
Cross, when Serge is in Chronopolis. He finds a diary, and the explanation
that pops up when you hit the action button is taken from Radical Dreamers.
For more information, check out http://demiforce.parodius.com/rd/. The web
page has information about a fan translation in the works. The coding has
been done; now all they need is translators.