IT! THE TERROR FROM BEYOND SPACE (1958)

 This is basically the blueprint for the movie ALIEN done in full 50's rubber-suited monster glory. It takes place in the far flung future year of 1973 when space travel will finally be perfected.It takes your generic monster on the loose story and puts him on a spaceship leaving Mars. Mayhem ensues. It's all fairly well done for this era and has always been one of my personal 50's favorites that I fondly recall watching back on TV as a monster kid before they drastically cut down on the showing of black and white stuff.  The creature's look itself reminds me a bit of THE MONSTER OF PIEDRAS BLANCAS which is another of my fav 50's B-movies.