It’s a common misbelieve that aliens should look very different from us, so when mentioning aliens with two legs, two arms and a head people may think that this is unrealistic. But is it?
Let’s think about that for a while. For example why do you think that the human race became the most intelligent one on earth and also the one most capable of using and making advanced tools? Well, that’s mostly because we have the perfect body for this; the perfect body-design for letting us evolve like this. You wouldn’t imagine a horse building a rocket would you? Because it would be very difficult for it with its claws and the way its body is designed. So that’s why I believe that the race evolving on other planets that gets a human like design first will be the race that has a much higher probability of becoming the race that master space travel on that planet. But sure, there might be exceptions.
But still they may be very different in how they experience the world and how their body functions, just like we see many differences in those areas in races here on earth. For example some animals can see into other wavelengths (the infrared and/or ultraviolet) and some animals (bats, dolphins) can use echolocation to map the surroundings, etc, etc. So aliens may have advanced in areas where we humans have not. I personally believe that they may have a higher spiritual understanding than us too and knows how to benefit from this, just like psychic people on earth for example or twins who say that they can know when each other one is in danger. Maybe this (and more) is common for aliens.