Gemini and Sagittarius is quite a visionary couple. One part provides the ideas and whims, and the other broadens and philosophizes - Gemini typically being the former and Sag the latter. While these two have many many things in common, they are also zodiac opposites. However, what the reputed opposite nature of Gemini and Sagittarius actually amounts to is a little unclear. Basically, it relates to the fact that Gemini is detached and strongly aware of detail and nuance, while Sagittarius is a blunt enthusiast, somewhat fanatic and more whole-oriented.
Also, for Sagittarius all ideas have a deeper meaning, and are more often followed through. Gemini loves ideas and thoughts only for what they are and feel no overwhelming need to act upon them. Gemini and Sagittarius are quickly drawn to each other but can steer away from each other just as quickly and easily. There is great physical rapport in most cases, for Gemini is ignited by Sagittarius' passionate ideals and displays of appreciation, and Sag is fascinated by the ever changing nature of Gemini imagination. A sparkling learning-situation, and sometimes a fabulous romance.