I was sent to earth by my people to study earthling interactions. My real form would make most earthlings scream in fear so I must use this weak human form during my time on this planet.
We do not wish to make direct contact because your leaders would probably end up using a nuclear device in fear, we are immune to such primative weaponry but your species would not fare so well, so for your sake we stay hidden, sometimes even as pets, watching you.
I cannot go into detail about my race unless this thread gets lots of flags and stars. Only then can I tell you more.