When looking for a simple fold, one’s attention naturally falls on a torturous corrugation-based model that takes an age to fold (not):
This is Maarten Van Gelder Caterpillar – an exhaustive corrugation executed on an 8×1 rectangle (although I think it would be more effective on even longer paper).
The series of collapses, sinks then reverse folds and then some shaping at the ends is exhausting, the result is fun to play with as it flexes and twists and turns in ways that these photos fail to capture.
I found the diagrams for this on a Russian Origami Society website, thank you Google translate.
Any chance you could share the instructions you used to fold this? I have been trying to fold this model using the instructions here: http://www.origami.cz/Pdf/caterpillar.pdf and I cannot figure out how to get the folds between steps 3-4 and probably 5-6.
That looks exactly like the instructions I followed. The initial collapses are things like waterbombs and preliminary (square) bases, you then pre-fold flaps and open sink the edges to shape the body and enable the feety things. Look carefully at the lines on the diagram – dotted lines are VALLEY folds, dot-dash lines are MOUNTAIN folds. Play on a scrap of paper until you get the collapse, once you get it once it will seem easy (because the model just then gets you to repeat it as many times as you have paper for.