The Colossus costume was eight feet tall, weighed 160 pounds and was made from burlap, plastic, rubber and fine chicken wire. Inside, there were batteries, cables, air tanks and oxygen tubes.
It took stuntman Ed Wolff (who was 7 foot tall) 40 minutes to climb in and out of his Colossus costume so a special rack was built where he could rest whilst still in costume in between shots.
The funeral sequence had to be reshot because actor Ross Martin, who was in the coffin, fell asleep and his snoring drowned out the recorded dialogue.
The film features an unusually restrained piano score by Van Cleave. This was not so much an artistic choice but brought about by a musicians' strike.
The screenplay was written by Thelma Schnee, the maiden name of Thelma Moss, who would go on to become a famous parapsychologist.