The crossover is a tried-and-tested trope in gaming. Ever since Alien met Predator, Freddy fought Jason, and Kratos stepped into the Soul Calibur arena, characters from fictional universes have been more than happy to meet up. And do more than say 'hi'.

So, while they're rife in gaming at the moment - with Pokemon Conquest (a tactical mash-up of Pokemon and Nobunaga's Ambition) and Professor Layton vs Ace Attorney on the way - there are plenty of historical examples of top-notch gaming crossovers to keep fans of mash-ups satisfied.

To celebrate the impending release of Pokemon Conquest, we looked at portable gaming's greatest crossovers. Hold on to your lore bibles - this is about to get messy (or non-canonical, more likely).

Ultimate Marvel vs. Capcom 3 (Vita)


Games and comics go together like Paula Abdul and MC Skat Kat. That's why we've had Ryu beat up The Hulk, and Batman go to town on Sub-Zero. Ultimate MvC 3 on the Vita is one of the best, mostly due to the ludicrous roster of Capcom characters.

You've got a wolf sun god from Okami, a valiant knight who strips to his undies when hurt, and a defence attorney who only really attacks by accident.

Wario Blast: Featuring Bomberman! (Game Boy)


If the intro to Smash Bros Brawl is any indication, Wario can cause a megaton explosion with just a little bit of flatulence. But, back in this monochrome mash-up, Mario's archrival needed help from gaming's most famous suicide bomber (until Angry Birds, anyway).

Its very much a Bomberman game (Mario's nemesis is not even in the Japanese version), as you lay explosives to trap and kill enemies.

SNK vs. Capcom: Card Fighters Clash (Neo Geo Pocket Color)


That's right - the two biggest names in fighting games. King of Fighters vs Street Fighter. Two bare-knuckle brawlers, stepping into the arena for this Neo Geo Pocket card game. Wait, what?

That's right: a game with Terry Bogard and E. Honda that wasn't about beating the snot out of each other. Not that Cardfighter's Clash wasn't a little gem of a crossover strategy game, mind.

Battletoads/Double Dragon - The Ultimate Team (Game Boy)


"When a battle-cruiser the size of a city smashes out the moon, you can bet it ain't gonna be makin' no social calls." That's the entire setup to this barmy crossover brawler.

In play, it's your standard beat-'em-up. You can play as Rash, Zitz, Pimple, Billy, or Jimmy, and your aim is to beat up bad guys on the deck of an intergalactic spaceship.

Mario & Sonic at the Olympic Games (Nintendo DS)


Sega's iconic hedgehog and Mario's legendary plumber had been at each other's throats during the entire 16-bit era. So, it was pretty bizarre to see the pair put their differences aside for this sports-themed mash-up.

Not that the events themselves made much more sense. Sonic - faster than the speed of sound, apparently - can be bested by fatty Wario in the 100m dash. Go figure.

Konami Krazy Racers (Game Boy Advance)


Konami pipped Mario Kart to the post when its own kart racer was part of the GBA's launch line-up. It featured loads of heroes and villains from games gone by, including Castlevania's Dracula, Metal Gear's Cyborg Ninja, and a whopping great Maoi head from Gradius.

A follow-up iPhone version contained even more characters, including Frogger and Silent Hill's terrifying Pyramid Head.

Kingdom Hearts: Chain of Memories (Game Boy Advance)


An improbable mash-up involving Final Fantasy and Disney deserves an equally improbable backstory. Legend has it, Square Enix producer Shinji Hashimoto randomly met a Disney executive in an elevator - and this here crossover was born.

This sprawling, convoluted RPG universe features Fantasy mainstays like Cloud and Sephiroth, alongside Disney dudes like Stitch, Tron, Ariel, and Jack Skellington. The franchise director wants to add Pixar heroes into the mix next.

Mario Slam Basketball (Nintendo DS)


If you were going to put a bunch of Final Fantasy heroes into a game, who would you pick? Cloud? Squall? Vaan? Try Moogle, Cactaur, and White Mage.

Maybe Square Enix thought the six-foot-tall Adonis heroes of Fantasy lore might have an unfair advantage in this frantic basketball spin-off. Especially against squat Mario heroes like Yoshi and Toad.

Lego Batman 2: DC Super Heroes (3DS, Vita)


Anybody who's anybody has crossed over into the Lego universe these days. Jack Sparrow, Indiana Jones, Harry Potter. They've all been cast in plastic and stamped with an embossed Lego logo.

But, Batman's second outing is one of the best Lego crossovers yet. Not only does it include a huge cast of DC characters (including Superman, Wonder Woman, and the Green Lantern), but it gets full voice acting and better puzzles.

New International Track & Field (Nintendo DS)


Once again, Konami delved deep into its back catalogue to find a bunch of old icons for this sporty crossover-cum-remake. So, you can play as a random athlete, or do the hurdles as Simon Belmont. I know which one I'd choose.

Alongside the main characters (including Sparkster, Pyramid Head, and Solid Snake), there were bonus levels and cameos galore.