The distortion, known as fasciation, is a freak of nature, and often looks like several stems have been fused together. It's a rare phenomenon and does the plant no lasting harm. It can develop on a range of shrubs, flowers and perennials. The cause could be environmental, such as the weather, or a pest attack that causes physical damage to the plant. Some fasciated plants are actually quite attractive and have led to varieties known as cristates. These include forms of ferns, cacti and succulents, such as Sempervivum arachnoideum cristate, and the cockscombe celosia, Celosia argentea var. cristata.
Misshapen and flattened stems, leaves and flowers.
In most cases fasciation is temporary, so just enjoy it for its curiosity value. If it offends you, prune out the affected parts. In a few cases genetic mutation is the cause, and the deformity will be permanent.