If you are getting fry from a guppy, they are not endlers. they may be a cross because as others have noted they will cross rather too readily. To get more info on endlers, try endlersrus. There are people there who are quite knowledgeable about them including two professional breeders. Most of us who keep endlers can tell rather quickly what we are lookin at. Its no mystery once you really look at a guppy and an endler side by side. The endlers, as has been said, resemble wild guppies more than fancy guppies and as others have pointed out, some of the crosses can be quite stunning. In my opinion, calling a platy a sword does not make it so and calling an endler a guppy also does not make it so. In both cases crosses can be made and produce viable and fertile offspring, in the case of the sword platy the offspring is called a variatus.