Gosei Wonder is Goseiger’s movie-exclusive robot from the short film Epic on the Movie… which I haven’t seen, so I don’t really know much about it. It’s not a personal favorite in the Goseiger arsenal… and that’s really saying something given that this show also features an ostrich robot that transforms into a helicopter hat for a sentient arcade machine.
Movie exclusives typically get a quick appearance in the show these days, so in this episode the Goseigers get the ability to summon Gosei Wonder (again, I guess?) after their boy sidekick Nozomu prays really hard for his mom not to die in a horrible train wreck. This episode skips having its own monster of the week so Gosei Wonder can team up with Gosei Ground to fight Metal Alice, who is trying to spread terror through Japan by sabotaging its mass transit systems.