The PCs enter a tower set up like an alchemist's lab. A potion can be seen brewring on the apparatus and filling up a large beaker with a glowing, blue liquid. A rack of similar potions stands next to the apparatus, already sealed and corked.
These are a modified type of levitation potion and have a sweet, fizzy taste. As soon as a player drinks a full potion, the drinker will begin to rise uncontrollably at a rate of 1 foot per second. If the potions are drunk in the tower, the drinker will have two minutes before he hits the ceiling where a razor sharp fan blade is spinning (instant death, no save).
Genre saavy characters may attempt to belch, to bleed off the gasses that provide the levitating effect. This will not work! Gas can only be bled off through flatulence.
A character who attempts to fart will succeed automatically on his first attempt. Roll a constitution check for every attempt thereafter (the PC may make 6 attempts per round). A fart will reduce the character's altitude by 20 feet for the first 5 successes. After that, the character will lose 30 feet for every successful fart. At 10 farts (the magic number), the character will continue to descend gently all the way to the ground. A character who makes an 11th successful fart will soil himself as the magic cuts out completely, and will plummet to the floor below, taking damage for the remaining distance. Altitude can easily be tracked with a simple line chart.
If any player is slain by hitting the fan or falling to the floor, a group of orange-skinned, 3 ft tall humanoids (treat as halflings) will filter into the room and perform an ironic song and dance routine.
The alchemist, Willhelm von Wonka, has left his notes scattered about haphazardly. If pieced together (takes about an hour), the recipe for these "Fizzy Lifting Drinks" (and details regarding their use), can be learned.