And although the game quickly slips into a familiar structure, alternating exploration, puzzles, and bosses, the sheer variety of Alphadream's offerings ensures that it rarely lapses into predictability. Like the previous titles, Inside Story is still a brilliant introduction to the baseline mechanics of RPGs, but it's something of a genre mutant at the same time. It flips between rhythm action elements in the game's sprightly turn-based combat - while the basic attacks and emphasis on timing remain unchanged from the past two games, specials have been greatly extended, and Bowser comes with a whole new range of moves - to anything from an unexpected riff on Ikaruga, falling block puzzles, and massive side-scrolling rumbles in which you hold the DS like a book, launching attacks by swiping the screen and blowing into the microphone.
The scenarios match the shifting mechanics at every turn. Aided by some of the best localisation in any game, the script is a comic treat, filled with blustery courtiers and a very strange block-headed Frenchman, while the plot sees you dodging creepy intestinal parasites one minute and beating up an entire castle the next. It's a game in which no narrative twist is too stupid or unlikely to be incorporated, a screwball comedy in which series clichés are wrung dry, and while it's not quite as cameo-heavy as the deliriously self-referential Superstar Saga, it still has time for some unlikely nods along the way.
Fortunately, the whole thing doesn't look as disgusting as it sounds, either. Bowser's internal system is a brightly-coloured cartoon fun-house with little to be squeamish about, filled with sparking dendrites and glockenspiel bones, patrolled throughout by swarms of quirky enemies, while the over-world is classic Mushroom Kingdom whimsy - a patchwork of creepy forests and blazing sands, home to meatier foes for Bowser to tackle. Few game series have embraced pinks and purples as thoroughly as this one, and Inside Story is perhaps the artistic high water mark - every fresh sojourn through the monster's endocrine system turning up some delightfully squishy sights, each new boss battle filled with yet more wriggly animations.
Ultimately, Inside Story reminds you that the best adventures are often a matter of trust. Alphadream's games work because you can let them take you on their bizarre, comical journeys with no fear that you'll be bored or annoyed along the way. You can trust the developer to balance an approachable RPG system without gutting too much of the complexity (if anything, tweaks made to the levelling and item management mean this is the deepest Mario & Luigi yet), and you can trust it to deliver intricate puzzles without resorting to sheer fiddliness. Traditional issues remain - the opening few hours are weighed down with too many tutorials, perhaps, and the boss fights remain slightly long-winded, too often coming clumped awkwardly together - but genuine frustrations are rare.
Superstar Saga was, very quietly, one of the best games of its generation, sadly appearing too late in the GBA's lifespan to be much more than a cherished secret. Partners in Time was similarly smart but not quite so engaging, possibly because the inclusion of the Mario babies overburdened the controls while offering too little reward for the extra hassle. That's not the case here, however: the brother's old enemy is a triumph precisely because he provides such a contrast to them: he's a bullish idiot who allows you to enjoy your blunt powers with very few limitations. Inside Story is absolutely a return to form, in other words - and, in the end, you've got Bowser to thank for that.