There are so many great one-liners in Head. Among my favorites are:
"Well, son, nobody lends money to a man with a sense of humor."
"Let's you and me go somewhere where we won't bump into each other anymmore."
"So you don't see the connection between government and laughing at people?"
"The tragedy of your times, my young friends, is you may get exactly what you want."
One of the really fascinating things about Head for Monkees fans like myself is how the individual members of the Monkees venture out of their usual roles. Micky Dolenz and Mike Nesmith remain their TV characters, but Micky's craziness and Mike's cynicism are taken to new extremes. Davy is transformed from teenybopper heartbreaker to (at times) a bratty punk with a violent streak, and Peter is transformed from a dummy to a zen mystical peacenik.
The biting sattire of everything about the late 60s is another thing that makes this movie stand out from the pack. In addition, it may well be the most psychedelic film ever made.
In short, it's everything Magical Mystery Tour should have been and a good bit more.