Contactees and abductees sometimes report encountering shape-shifters that can change their appearance instantly. Most of these, and especially the reptilian shape-shifters aren't real shape-shifters: they cannot actually materially change their appearance. Instead they use mind control techniques, and project an image, so one, as if hypnotised, sees what they want one to see. This technique is often used by some reptilian aliens to freely walk on Earth, without being recognised. To some alien species, this ability to impose their will is innate. Others can establish the same effect by using devices that were designed specifically for that purpose. (Some reports say that the US Government had already obtained such devices but as yet has been unsuccessful in modifying them so they can be used by humans).
Apart from these fake shape-shifters, there are genuine shape-shifters, too. Most, if not all, higher dimensional beings, as well as some species that are not physical as we know it, can appear in any shape they want to, or you want them to, because with their thoughts they can manipulate matter and energy. They are pure conscious energy, and can take any shape they want to when materialising in a physical reality. Often they will choose a form that is comforting or familiar to the individuals before whom they will appear.
This topic was copied from the HyperBase and is likely to be revised.