The Forgotten(1997)

There's been an accident. Someone crash-landed a Yeerk Bug fighter. And the Yeerks have been trying to cover it up—quickly. But not before Tobias spots it. So the Animorphs and Ax decide to steal the ship to show the world that Earth has been invaded.

That's when things go terribly wrong. Before they know it, Jake, the other Animorphs, and Ax find themselves in another place. Another time. And there's no way home...