There is almost certainly life in some form or another amongst the (likely) millions or even billions of planets that have liquid water.
However, it is a, well, astronomical, leap to go from "life elsewhere" to "life elsewhere has jumped into a spaceship and is joyriding around earth".
Ignoring the virtually insurmountable physics problems.....
Any life-forms intelligent and powerful enough to figure out how to traverse trillions of miles safely and easily - well, why on earth (oops) would they be interested in comparative protozoa like humans?