It's a Monty Python thing - The Knights who say Ni were on a quest to discover the Great and almighty shrubbery. King Arthur is involved, as is cutting down trees with a herring - it's all too silly for words.
I teach 17 years old who have not heard of Spike Milligan or the Goons either. It saddens me that there are people who have not heard of the Knights who say Ni or that do not immediately associate them with shrubberies. Their young lives are only interested in whats new and they have passed over the sublime, pant wetting, side splitting humour that unites us 50 somethings. Their loss.