You have a long strip of paper, one piece of tape, and some scissors. You must create two paper rings that are linked. The catch is that you must use the tape before touching the scissors, and you may not tear the tape or paper.
(In reply to Moebius strip -spoiler
by Ady TZIDON)
It is even easier:
twist the strip once, and start cutting at 1/3 of the width of the
strip, along the ring. This will give a ring with one half-twist and
the same length as the first strip, through a ring of double length and
with two half-.twists