The Sisters Trick
Start by putting one red Queen on top of a regular poker deck, and the other red Queen at the bottom, both face down.
Next, give the two black Queens to a spectator. Start dealing cards off the top of the deck, laying them in a face down pile on the table, until the spectator tells you to stop.
Have the spectator put the first black Queen, face up, onto the pile (opposite to all the cards you have been laying down.) Drop the remainder of the deck in your hand face d
wn onto the black Queen. (So the only card facing up is the black Queen.)
Next, repeat the process above, having the spectator put in the other black Queen, face up, and drop the remainder of the deck on top of the black Queen, again face down. Have the spectator cut the deck, and complete the cut.
Now announce that without any help from you the spectator was able to find the black Queens' sisters. Simply go to the black Queens, take them out, and the cards immediately above each will, of course, be the red Queens.
You have shown the spectator the Sisters Trick.