This is something I had in mind some years ago and wanted to draw:

1. Just go to the park (you can also try at the beach if you don't mind the sand or at the pool) and look for women having a sunbath facing down.
2. It's time to use the shrinking serum and sneak towards their soles.
3. Once you find one of them that has slippery feet (sweat, skin oil or water) find a way to her ankle.
4. Jump.
5. Slide down her sole.
6. ???
7. Profit & repeat.

Hope you like it ;D