When I was about seven years old, my dad built a shed for his tools in the backyard. I appropriated the small building as a clubhouse.
During that mid-1960s time period, there was a cartoon show that featured a very cool clubhouse, with a barrel for an opening, and an adjacent tree that was part of the clubhouse. The name of the show had faded from memory, and I didn't remember enough even to do an internet search.
But serendipity! A Facebook friend commented that she had the theme song of this show stuck in her head--and that she had forgotten the racist depiction of the Native chief whose voice was a train horn. Then about a week later, another Facebook friend posted something about the show.
According to imdb.com, "The Funny Company" began in 1963. (https://www.imdb.com/title/tt0299913/) Here is an article about the show by a WGN-TV watcher. The show had been created to fill a dearth in educational programs for kids. I never would've remembered that. I liked the clubhouse---a social precursor to the man cave or the she shed.