This was in his biography about his days on Laugh In. I remember actually seeing this episode and the thought of it still makes me laugh:
Gibson was best known as the poet, holding a large flower and beginning his brief recitations with his signature catchphrase, "A poem, by Henry Gibson."
"He wrote all those himself," Jon Gibson (his son) said. It was a point of pride that he only read poems that he himself wrote."
During one of his frequent guest appearances on the show, John Wayne spoofed Gibson by coming around the wall holding a flower and delivering "A poem, by John Wayne."
"Roses are red, violets are green," Wayne said, "Get off your butt and join the Marines."
Can you imagine being spoofed by John Wayne?! How cool is that?!
I'll miss ya, Henry.