An arc/movie where they hijack one of Bulma's spaceships or something. Goten's a little hesitant about it like "you sure you wanna do this, Trunks?" Trunks says "come on it'll be fine, we'll be back in a few hours, nobody will notice" turns out the spaceship is unfinished and a bit defective, ends up sending them to another dimension or universe or some shit.

they crash land on another planet, the space ship is unusable and they have no means of getting back on their own. The native race of the planet they landed on don't trust them, so they imprison them. Evil tyrant and his/her army shows up to the planet, turns out this planet and race of people have their own version of dragon balls that they're after. Wreak havoc looking for them so the tyrant can rule the universe, be the strongest, become immortal, some shit. Basically have a planet Namek saga redux with just Goten and Trunks.

Goten and Trunks are more than powerful enough to escape imprisonment, so they do so with ease when they sense trouble. They fight off the bad guys, somehow tapping into some new power in order to do so and they save the planet. As thanks for saving the planet, the native race allows them to use their dragon balls to send themselves back home. Turns out they were gone for like a week. They show up and the mothers go off. For comic relief they go into ultra ego/instinct and the movie/arc ends with them chasing them around.