For a number of reasons a mistake can be made in a plant's growth. One of these is fasciation, a condition in which the growth is flattened, ribbonlike, or fanlike. I have seen and taken pictures of Rudbeckia Denver Daisy several times over the last few years, and this cultivar seems to be prone to the condition.
Zinnias are somewhat prone.
I have read that the large, oddly shaped beefsteak tomatoes represent a form of fasciation, as do the crested celosias. This is also true of the exotic looking crested cactus. The possibilities are seemingly endless. It would be fun to start a thread on fasciated flowers.