Name of old space game

Hello,
I have been trying to find the name of a game I played as a child. It was a space shoot-em up type game. Your ship sat at the bottom middle of the screen and you could move right to left while the aliens scrolled down towards you. The aliens changed during every level and after awhile it was almost as if it ran out of alien shapes and started using anything such as ice cream cones, sunglasses, pizza slices, etc. Anyone remember this strange game?