Previously I only really watched Hawaii Five-O in reruns when I was a kid.
At the time I was watching stuff like Magnum PI, and came across reruns of Hawaii Five-O while I was channel surfing. Not knowing any better, I thought they were earlier episodes of Magnum.
I think in an early episode of Magnum,
they make reference to McGarrett, and I remember reading that the show's producers tried to prevail upon Jack Lord to make a guest appearance, but he went into retirement after Five-O
ended in 1980 and stayed there for the rest of his life.