A/N: Yes, if you haven't guessed by now, it's a Doctor Who/Den-O crossover. This has been in my head for a while now. And now I'm finally getting around to writing it. This story also deals with the alternate universe travel that Decade did.

Oh, and Koutaro keeps his blonde hair.

The Doctor and Donna browsed the library looking for something. She trips over a pool stick. "Donna, this is no time for lying around. We have a book to find." The Doctor helps her up. "Any reason for this?" She holds up the pool stick. "Oh, that's where it was."

"Why is there a pool in the library?"

"Can't have a good book while swimming, or have a good swim while reading?"

She shakes her head and asks, "What book are we even looking for, anyway?"

"A book about a legend."

"Legend of what?"

"A train that can travel through time."

"Like Back to the Future?"

"Not entirely. You see, this train travels through the sands of time, an alternate place to travel through time. It's like the Time Vortex, but not."

"Can't we just find a book about the sands of time?"

"There's a sands of time chapter in the book. Now, come on. I think it's close by."

"What's the train's name anyway?"

"I really don't remember, since it comes from an alternate universe."

"Then how do you know about this?"

"Because I got the book in my 4th incarnation in the alternate universe section."

"Can you at least try to remember?"

The Doctor stops in his tracks and thinks. He raises a finger and says, "Den-Liner."

Meanwhile, on said train, Nogami Ryoutaro and Kohana have reboarded for Owner had to tell them something important. They still retain their young appearance. "Naomi, where is everyone?" Kohana asked noting the absence of the Imagin. "They went out to get Ryoutaro." Naomi answers. "But I'm right here." Ryoutaro points out.

After a few seconds, Ryoutaro runs out of Den-Liner to catch up with the Taros. He can only think of one place they could be.

"No, Ryou-chan went out an hour ago. He hasn't been back since." Airi tells the Taros. The Milk Dipper was closed for the day due to some more renovations. "Tch. Thanks anyway, Nee-chan." Momotaros cocked his head. "He probably got lost in another dimension again." Urataros sipped his mug of coffee and slapped Kintaros on the head. Kintaros then wakes up.

"Again?" Airi asked. "Blame Tsukasa for that one. His travels enabled all of us to travel the dimensions at will. With Ryoutaro's bad luck in the mix, he can't travel through them at will." Kintaros folded his arms then goes back to sleep. Ryuutaros, on the other hand, was too busy staring at his drawing of Airi he made a few years ago. "Brat, we're going." Momotaros taps Ryuuta's shoulder. He sulks at the thought of leaving Airi, but goes off anyway.

"Tell me when you find him!" Airi waves.

Donna pulls a book out from one of the shelves. "Imagin?" She asks the Doctor as another book falls out. "From the planet Imaginate. They've been working on a way to make a future point in time on Earth theirs. They still haven't found a way to even get to Earth, though." The Doctor picks up the book that dropped. "Found it!" He smiles and shows Donna.

He takes both books, and they run back to the console room to read it.

A dimensional wall opens. "Did you do it?" Momo asks. "No." Urataros answers. They shrug and walk through to another dimension. As they walk through, they don't hear Ryoutaro chasing after them. He runs through the wall, and as he runs through, he doesn't hear the sound of Den-Liner's whistle marching through until Koutaro pulls him in.

"Koutaro!" Ryoutaro shouts. "Owner went out to get me and Teddy. Seems this is big." Koutaro says. They walk into the dining cart. Owner is eating fried rice while Teddy and Kohana were catching up. "Seems there are more Imagins attempting to cross dimensions." Owner explains.

"Then why are we crossing dimensions?" Ryoutaro asks. "Because the Imagin attempting this are from a different dimension."

"Are we going to that dimension?"

"We're the one who opened up the wall."

"To where in this dimension, exactly?" Koutaro asks. Ryoutaro looks out the window. "We're in space!" Kohana, Naomi, Koutaro, and Teddy look out too. "Ah! Momotaros-tachi!" Koutaro points to the Imagin swimming in space.

"How can we even breathe?" Ryuutaros asks. "We're Imagin. We're made from sand." Kintaros answers. "Den-Liner!" Urataros shouts. The other 3 turn to see Den-Liner. Momotaros swims over. "Hey! Open up!" He bangs on the door, which opens. The Taros enter and regroup in the dining cart.

"So, why's Koutaro's hair blonde?" Momotaros asks.

Now, on the planet Imaginate, the leader of the Imagins announces, "Now, with this technology, we can cross dimensions and make every Earth's time our time." This leader is a red oni. Behind him was a blue turtle, a yellow bear, and a purple dragon.

The train and blue box of time, Den-Liner and the TARDIS. Will their next journey be the past or the future?

Theme: Climax Jump Den-Liner Form

Jikan no nami wo tsukamaete

Den-Liner time travels through a portal.

Ima sugu ni yukou yakusoku no basho

Den-Liner travels through the time vortex. The actors' names are listed.

Genkai mugen iza tobikome

The TARDIS travels alongside.

Climax Jump!

Both time traveling things go further into the vortex, and the logos for each respective show appear, then disappear.

ii jan! ii jan! sugee jan?! ii jan! ii jan! sugee jan?!

The title of this fic appears and disappears.

kanaetai yume ga aru nara

Calendars fall. That, and the sonic.

In a watch-type frame, The Doctor, Donna, the Taros, the Nogamis, and Teddy run through a corridor.

shinjinakucha negatta hibi wo

An adult Ryoutaro slowly turns, and de-ages when turning.

In the frame, Kohana punches Momotaros, who falls. The Taros behind him fall too, making a domino effect.

Catch the wave

The Taros dance in front of microphones.

mayoisou na toki kanarazu

The TARDIS materializes on Earth, with Den-Liner and Zero-Liner following.

omoi no tsuyosa ga michibiku

Momotaros and the red oni Imagin have a slap fight.

KIMI ga nozomu mirai sude ni

The Doctor sonics the planet of Imaginate.

In your hands

Zero-Liner's whistle is heard.

hajimari wa itsumo totsuzen

Kohana fights some Imagin alongside 5 old Den-Os, a Zeronos, and a new Den-O.

unmei wo tsurete yuku Time tripin' ride

Momotaros chases Urataros around the TARDIS console. The Doctor is not impressed.

dare yori takaku kinou yori takaku

The Doctor fixes his tie.

The Doctor and Momotaros do the "Ore Sanjou" pose.

Climax Jump!

Silhouettes of the cast are seen jumping.

ii jan! ii jan! sugee jan?!

ii jan! ii jan! sugee jan?!

The TARDIS and Den-Liner travel through the sands of time with the Imagin dancing.

A/N: Originally, this story was to have the 11th Doctor and Clara, but changed it to the 10th Doctor and Donna because it felt right. I mean, come on. I wrote the Doctor in this chapter to have some attitude of both his 10th and 11th incarnations. Might as well put Donna in there for wit and the fact that I know nothing about Clara yet.

An original line had the Doctor noting that he rebuilt the pool in the library, go figure, but then he became Tennant.

Anyway, of course Zeronos is in this. It's that big of a deal for him to be there. Debating on whether it should be Sakurai or Yuuto.

I'll write a DW crossover story with Eleven and Clara some day. For now, enjoy this little thing.