My first set of clipless were these on a mountain bike:



The cleat was kind of like an SPD, but bigger. Crummy pedals - hard to get into, easy to accidently release, hard to intentionally release.

Anyway, my first ride on them was on a greasy-slick wet trail with plenty of rocks and roots. I fell over so many times. I don't know if you'd say it was "because" of the pedals... Eventually, I got some SPD clones, and they were much better.

By the time I began riding on the road, I had mastered clipless. No falls on the road.