I’m sure the answer is ‘yes’, but have we talked about this? Has Nona Hendryx (who wrote this tune) ever been properly co-credited for the P releases that featured this quote? The original studio version of Slop didn’t feature the “Space People” refrain, but several live releases as well as the “Hardcore.Jollies” version feature this stanza.
Based on your references, I guess that somewhere in late 74 or early 75 is when it was added. I’m guessing it was Fuzzy’s idea, but I’m only guessing that because he was the vocalist who sang that part at the time.