Ann,
The most obvious scenario that comes to mind is a steep turn at fairly slow speed... the wing loaded and near critical angle of attack when the use of rapid (full?) aileron (deflected down) to roll out causes the inside wing to exceed its critical angle of attack and stall... tucking under rapidly as the outside wing is not stalled. This stall condition is further accelerated if by chance the pilot was using 'inside' rudder during the turn, causing the aircraft to skid... thus increasing the angle of attack on the inside wing also.
I often use a PA-18 to teach spins and this is one of my favorite 'gotchas' that I use... setting the student up subtly... and leaving a lasting impression of how critical coordination is when operating the aircraft to its extreme envelope. The stall from a moderately banked (base to final) turn with inside rudder (skidding) is often very violent... resulting in a spin with an extreme nose down attitude that requires a lot of altitude to recover from.... usually as much or more than 500 feet.
Because of this, I am a very strong advocate of teaching dutch rolls and full oscillation stalls (aka falling leaf stall) to make the students rudder control become instinctive... connecting the eyeballs to the feet, leaving the brain out of the system. If the nose doesn't yaw, the aircraft can't spin. Knowing how to do a spin recovery does little good below 500 feet agl if you don't recover before impact. Spin PREVENTION is the key to surviving in Cub flying.... and that means yaw control must become instinctive. You can hit the ground stalled (if straight) and survive if the aircraft has forward momentum. Hitting the ground during spin rotation is usually fatal.
I personally (within 50 yds) witnessed a fatal Pitts crash when an engine failure caused the pilot to try to return to the airport. The aircraft was 'bucking' as he tried to stretch his glide... only to spin from about 50 feet (only 1/4 turn) and impact nose first and burst into flames. Ironically... the aircraft landed in high corn. Had the pilot just pitched down and decided to ditch the aircraft, it most likely would have just flipped over and wrecked... with little, if any, personal injury.... Very sad. btw, the cause of engine failure was a small piece of rubber blocking the fuel line.
Hope this is what you were looking for...
John