inspired by Robert Baxter's Computer Cutie (and David Copperfield's version) of the trick,
but not confined to a poster. This is real life!

This example is a bit risqué, but it could be applied to many different themes,
I'm just using the girl because it's easiest. The lights in the tent fade up and down with each step in the process. (ie, the audience sees the shadow of the girl letting down her hair, and as she hands it out the tent, the lights in the tent go out. At each step the magician has the option of opening the front of the tent to show the changed girl. The magician talks about how he met a girl, things started to heat up. An innocent looking girl is shown sitting on a chair in the tent with her hair up. The magician closes the flap and talks about how things started to heat up.

The shadow of the girl takes out her pony tail (handing it out the hole (or top) to the magician) and lets her hair fall! (the shadow of the girl shaking out her hair, etc.) Then the girl hands the magician her shirt through a hole. Anyway, things continue, build up, until the audience thinks the magician is going to show them the skimpily-dressed girl. He tears down the flap and the girl's father is there with a shotgun (or some other surprise, unanticipated ending!) I'm just using the example of the girl shedding articles of clothing, this could be anything. A person growing up, an animal evolving, whatever! It can also work backwards, where the magician drops articles into the tent instead of receiving them from whoever is inside the tent.