You’re thinking of Fiend Without a Face, which featured creatures that looked like flying brains (with attached spinal cords) and having antennae. What made it cool was that the brains were painstakingly animated, like Harryhausen’s creatures (although not by him). When they were shot, they sort of bled out thick blood.
The thing that impressed me most about*** Invaders from Mars ***when I saw it at the age of 10 or so was how the walls of the underground tunnels bobbed in the breeze as the actors ran through them. (They were made up of hundreds of party balloons inflated to simulate bubbles of silica subjected to laser blasting.)
I knew a guy who had two almost fully-inflated ones tethered together over his desk, the area around the uninflated tip being painted a darker hue. It looked like an enormous pair of boobs over his desk. Meant for inspiration, no doubt.