But, who were these original teammates?
Cliff was a race car driver and all around daredevil who took one too many risks, and his history before the Doom Patrol started in a back-up tale in Doom Patrol #100 (December, 1965) by Arnold Drake and Bruno Premiani, called "Robotman -- Wanted Dead Or Alive" subtitled "An Untold Story Of Robotman". This story dealt with Cliff's crash, and how a surgeon saved his life by transplanting his brain into a robot body, which made Cliff into a "Robotman-iac", sending him on a super-strength, anger fueled rampage through the city, looking for the doctor who did this do him.
Larry was a test pilot flying experimental planes, with his pre-Doom Patrol days being chronicled starting with Doom Patrol #106 (September, 1966) with "The Private World Of Negative Man" by Arnold Drake and Bruno Premiani, where the pilot flew through a radiation belt at a high altitude, becoming radioactive and gaining the ability to manifest his consciousness as an energy being that can fly for up to sixty seconds at a time. His radioactivity would have isolated him from all other humans, if not for radiation-proof bandages invented by Dr. Niles Caulder; but the bandages isolate him from others, making him look like a mummy and a "freak".
Rita Farr was an actress, as well as an Olympic medal winning swimmer, so it's a shame her early days didn't get individual coverage like the other members during the original Doom Patrol run...
Niles was involved in the origins of all the previous members, but his origin was what created the need for the team, as revealed in Doom Patrol #88 (June, 1964).