Paradox Trophy in Deponia

Missable!

In the Concourse area of Act III is a stack of pebbles. Pick one up before you leave the area. A little later on, you will find yourself in the Tower area, with a green pool in front of you. Throw the pebble into the water and enjoy both the cutscene and your new trophy.

If you missed the pebbles and are unable to pick them up later, this will also work with a piece of gum from the candy store.