The Aliens from the 1953 film It Came from Outer Space are a spacefaring non-humanoid race with a rounded body, a large single eye and several tendril-like appendages. They seem to travel in spherical ships and are able to alter their appearance greatly, although this might to be an illusory (perhaps telepathic) rather than physical ability. They also release clouds of smoke when they transform.
One ship of this species crashed on Earth in Arizona due to a navigational mistake, as they were heading to another planet. The aliens attempted to remain hidden and not draw much attention from humans for the time they needed to fix their ship. Unfortunately, they had to kidnap some humans in order to assume their form and replace them, so that they could infiltrate human cities to gather the materials they needed. The aliens' presence was noticed and an angry mob was formed to kill them, but the aliens managed to fix their vessel and release the hostages in time and left Earth. It is possible that they will return some day, when humanity is ready to make contact with them.
Overall, It Came from Outer Space was a very innovative movie at its time. It was one of the first sci-fi films to feature an intelligent, non-humanoid and non-malevolent alien lifeform. In an era when aliens were nearly universally portrayed as evil invaders, the creatures from ICFOS have no evil intentions at first, and the main reason for their secrecy and later hostility is because they don't trust humans. They know their appearance is considered grotesque and they know humans have a tendency to destroy what they don't comprehend.