Combine Duplo feet with regular LEGO I would like to place this Duplo pig directly on Lego bricks/pieces. I tried an intermediate Duplo 2x4 plate with Lego bricks underneath, but it doesn't look good. The problem is that Duplo feet surround the studs. Therefore, Duplo feet don't fit onto Lego studs. Is there an elegant way to connect Duplo animals' feet with the Lego world? 



@Uli found promising solutions, one of them is to use the Technic Engine Piston Round. It has some clutch power and at least transfers the issue into the regular LEGO world. Now I have to find a way to connect tow ball pieces to the rest of my MOC, Uli has provided some ideas.
I am still waiting for the bricklink delivery with 27448 tiles that Alex suggested in one comment of his answer. Therefore, I tried a less subtle solution:

This is the starting point: A DUPLO pig that needs to be put directly on LEGO pieces.


I decided to cut a DUPLO piece to regular LEGO size. A DUPLO 2x2 brick was converted to a ...


... 4x4 tile, modified, with 2x2 DUPLO studs. My methods were crude (metal saw and cutter), but it worked quite well. There is only little height difference to the surrounding LEGO plates, and the clutch power is really good:


This is an approximation of the final goal to use the DUPLO pig as a figurehead in a LEGO MOC/MOD:


Edit: The 27448 tiles finally arrived, but there was no way I could get clutch power. I measured 9.3 mm for the diameter of the tile ring, and 9.4 mm for the DUPLO stud. This difference is enough to loose any clutch power. Even with 4 tiles combined there was no binding strength at all. Other DUPLO animals showed same results. A DUPLO human figure, however, could at least have a little bit of bonding when the ring is pushed into the toe area.