There are many instances where galaxies appear to be interacting with each other enough to cause obvious distortions of the galaxies that interact. These interactions may have a significant connections with the manner in which galaxies evolve with time.
The adjacent pair of interacting spiral galaxies in the constellation Andromeda at a distance of about 200 million light years is called Arp 273 (Source). The larger galaxy at the upper left is strongly tidally distorted. The companion (seen edge-on in the lower right) exhibits a relatively undisturbed spiral disk, but a luminous, star burst nucleus (one in which there is a burst of new star formation). The nucleus of the large spiral has properties indicating much less activity than the bright nucleus of its companion. Thus, the large galaxy has a modified disk but little evidence of damage to its nucleus, while the small galaxy has an undisturbed disk but a very active nucleus.