I always saw Bill Nye as a budget Mr. Wizard. Don Herbert had a style and presence which made scientific phenomena really seem like magic -- fascinating, but completely knowable. He engaged with kids and seemed genuinely interested in them, and he had a voice and diction like an old-timey radio announcer, so everything he said was clear and easy to listen to. (This is important: later in life I would take a college course with a professor who mumbled... in a Chinese accent. I did not do well in that course.)