So, after a brief period in the late 1960s and early 1970s when he replaced the monologue with a fictional one involving "multicolored rainbow roaches", he decided to do it only on special occasions from that point forward.
After a brief period in the late 1960s and early 1970s when he substituted the monologue with a fictional one featuring "multicolored rainbow roaches", he opted to perform it only on special occasions from that point forward.