Disclaimer: All ideas below are Creative Commons By-SA-NC. Write, draw, commission, alter, bend, spindle, mutilate, whatevs. But if you want to sell something based on it, contact me. Because I'll probably want a copy.
SUIT UP: Three people, three dinosaur costumes, trike, raptor, rex, red, blue, green, no particular order, Fox only, Final Destination. They are planning to go to a costume party, but start transforming. Despite spending 25 minutes just to get dressed up, they might not even make it to this club. Whether they never leave the house, or pull over on the road, is up to you.
I like the idea of them bursting out of their costume as the real thing grows in. I also like the idea of them ending up as archetypes. For example, if they end up as dudes - regardless of what they were before - they become twink, muscly, bear. Women could be amazon, matron, and teenager. And that's assuming they all end up the same gender. My third idea was that the three individuals all shift "one over" from what they actually are, whether build and/or gender.
Inspired by that Hyperbole and a Half strip.
Stretch Goal: They make it to the party, and start getting frisky with some of the other people there, and oh no it turns out the costume thing is contagious. Whether they get turned into more dinosaurs, or whatever costume they're wearing, is up to you, though I like the idea of a Diplo (no, not the musician) bursting out of a sexy Little Bo Peep/ironic cross-dressing Lady Gaga/hanging chad costume.
I LOVE NUCLEAR POWER: Inspired by that "Nukezilla" story by...Phen, which is related to the pictures by rykela (both on sofurry). Someone gets exposed to standard issue technicolor radiation somehow, and transforms into an anthopomorphic kaiju. In fright, they breath nuclear fire at someone else. This someone turns into a slightly different Kaiju, with the fire breath and some other power; let's say viral breath. So they breath into an airvent, and a room full of people succumb and are transformed themselves. The first person gets slightly larger, and the second person's power. As the people in the room transform others, the second person and the first get larger, as well as their powers. When the Tier 4's convert people, the Tier 3 that turned them not only gets their powers, but said T3's powers are distributed laterally to the other T3s. Alternately, each person up the chain gets their new powers as they convert others. 1 would get the Level Up immediately upon infecting 2, and so on.
Eventually, the first person is going to be the size of a skyscraper, and spewing nuclear fire and viral breath and cloaking and, I dunno, shooting eggs from their elbows. Keep in mind that their entire body is chock full of viruses, cough cough, so even their sweat changes people. Among other things.
That's right. Kaiju virus transformation Ponzi scheme.
Stretch Goal: Make it a wacky romantic comedy.
HEAT SLAVE: Someone lying on their bed, middle of summer, sweating under an entirely inadequate ceiling fan. Maybe they notice the fan's blades have weird markings on them, like magic circles. As they stare at it and their thoughts wander, their body starts turning to latex, studs and straps and stuff appear. So, by the end of the process, they're a latex-bound...something, possibly clad in a gas mask. Maybe the bed changes too.
Inspired by my love of puns and the temperatures where I live reaching 86 F/30 C ARE YOU KIDDING ME.
Stretch goal: Their roommate comes home, finds this sex doll on the bed, assumes it's a joke, decides to - wait.