Most tropical cyclones rapidly weaken over land, however, given some conditions (such as very wet soil/ground cover and tropical lower atmospheric conditions) they can sustain themselves or even intensify over land, in a phenomenon known as the brown ocean effect. So, is it at all possible for extreme "brown ocean" conditions or other potential factors to result in not only the maintenance but the formation of a tropical cyclone over land, either from an extratropical system or not? The intensity and duration of time that the storm would last without transitioning to water is irrelevant—even a few hours at tropical storm levels would be a yes.
No, it isn't possible for cyclones, hurricanes and typhoons, which are all different names for the same thing, to form over land. Storms can form over land, but not hurricanes, which draw their power from the sun-warmed ocean and rapidly lose their strength when they hit land. The power of a typical hurricane is immense, probably in excess of 50 megatons, which was the yield of the largest hydrogen bomb ever tested (by Russia).