[madbadgalaxyman (Robert)]

I am always happy to see another image of M66.

The complex morphology of this galaxy teeters on the
edge between normality and peculiarity e.g. the arm asymmetry between the two main arms is at the upper end of normal for a non-dwarf barred spiral galaxy, but the broader and much more chaotic arm shows highly unusual dust lanes at its faint end...... when it is imaged deeper than in your image.

There is also a Very Faint outermost "arm" that is seen in very deep exposures, an arm or tidal feature which has no counterpart on the other side of the galaxy, and which provides some evidence for a past interaction with N3628.

There is also a very unusual spur that sticks out of the main large-scale bar, beginning at right angles to the main bar.
This is extremely obvious in your image. Another interesting aspect of this spur is that it is very different in colour from the surrounding material.

cheers,
madbadgalaxyman

Nearly all barred spirals are "perturbed" in appearance, and arm asymmetry is the rule rather than the exception; it is just a matter of assessing the degree of perturbation in this galaxy.