It's not as howlingly bad as Plan Nine From Outer SPace but there are plenty of laugh inducing effects to sing your fly claws into but what do expect from a teensy budget and a director that was used to doing The Three Stooges Episodes with Shemp.Most of the cast strives for dignity in the face of a script that was hurriedly written and probably uncared for even though you do get the standard over the top moments that were in just about every 50's sci-fi. The effects are legendarily bad and many folks(myself included) have a fondness for them. Where else are you going to see a guinea pig with tiny human appendages? Glen Danzig of Misfits fame even writes about it in a song Return Of The Fly. "Return Of The Fly,with Vincent Price.You guinea pig,Return of the Fly,human hands and feet,Return of the fly." It's a lot of fun and one of my Saturday night TV chiller show faves as a kid.