Cultivars which are exactly alike?

With so many registered cultivars I wonder: are there any cultivars which are exactly the same in appearance?

I mean: say that you got 2 plants with a different origin and from one you know the name of the cultivar. You grow them for a whole year next to each other, same soil, same light, same water, same climate. Photograph them each month to compare them. If you don't see any difference at all, also not in small details like hairs on the leaves and in the flowers, would it be safe to conclude that they are the same?