The body shape of an organism should conform with the needs of this organism.
To any intelligent organism as less energy spent at locomotion better, then, this organism will reduce the locomotion structures to the minimum necessary that let the organism move and capture the necessary food to survive.
We should have in mind that as more structures to locomotion bigger the space on the brain used to coordinate the movement of these parts, reducing the space available to the abstract think. Therefore, more structures, less intelligence.
In the case of an intelligent organism that intend make a space travel the requisites will be even larger, because they need to have ability to make and use tools, a good motor coordination and capacity to carry objects of various formats from one place to another.
Based on this principle lets imagine an organism with only one structure that can be used to move or capture the food. What is the matter with this configuration? Well, firstly, or the organism moves or capture the food but not both at the same time. Then, to capture the food the organism need to move to a place where the food is or go to a good place and stay there, static, waiting the food pass near enough to be captured. This organism could not climb trees because have only one structure to grab and when this organism need move it upward will fall down, making only possible to organism eat things that can be found at ground level. You can deduce that this configuration is very limiting. Therefore, we should think about at least two structures to the same function.
Based on the previous paragraph, we can imagine that an intelligent organism should have two legs and two arms or four paws (while the front paws are capable to catch things the rear paws are used just to propel the body). But for that organisms that intend to make a space travel two legs and two arms are requested.
In the case where the organism need catch things with various formats an opponent finger is an advantage, such as in the last case described above.
Why not two legs and four arms? Simple. Because the benefits don’t compesate the extra cost at energy to sustain it and the extra space on the brain required to control.
Why not four legs and two arms? Same reason.
Therefore, a body shape like ourselves (two legs, two arms, a head and upright posture) should be the best option to any form of life that are capable to create technology and make a space travel, but differences in height, weight, strength, power and proportion should exists and will be determined by the environmental variables of the planet where the organism emerged and lives.
On planets with a heavy atmosphere or intense gravity those organisms should have strong muscles and low height, while on planets with a slim atmosphere and low gravity those organisms can have weak muscles and big height.