Wish

Wish is the grab-all for asking your Dungeon Master for... anything. If you word it right, and you haven't pissed off your DM lately.

In Dungeons & Dragons this is a spell, for the highest level of magic use. The full-on version (for mages) would be the ninth level in the classic rules; there's a limited wish for seventh. Clerics get a miracle in their highest level, the seventh. The scope of the effect is limited to those of similarly-leveled spells for similarly-leveled casters; limited wish will impose some additional provisos, quid-pro-quos, as you saw in Disney's Aladdin. Apart from that, what happens next is up to the DM's interpretation of what you said you wished for so... be careful.

Lower levels get access to this stuff through the usual Arabian Niiights methods, typically importuning a djinn or an afrit, or maybe a devil. In these cases, the fuckery won't be what the DM can get away with so much as what the djinn can get away with. Since in several suras of Islam, al-Shaytan himself was of the djinn race - we recommend you get your fine-print spectacles on.

Because even the Limit of Wish has always been too vague for many dinner-tables, not all groups allow it. Eldritch Might's second Book introduced an alternative: Extemporaneous Soul Magic.

In /v/ media, the Wishbringer game allowed a Wish to bypass puzzles that were too hard; this was the entry-level in interactive fiction Zork-universe play. Over in /tv/, besides Aladdin, we can recommend Wishmaster for a particularly assholish djinn.