From The Art and Popular Culture Encyclopedia
The term "humanoid" refers to any being whose body structure resembles that of a human. In this sense, the term indeed describes primates, as well as mythological creatures and artificial organisms (robots), especially in the context of science fiction and fantasy fiction. An android or gynoid is a humanoid robot designed to look like a specific gender, although the words are, in principle, synonymous.
Usually, a fictional humanoid species has the same basic body outline as a human, being bipedal with hands which include fingers and opposable thumbs, but differs in details such as number of digits, coloring, ear form, presence of hair, average height and weight, size of nose, form of skin, "extras" such as horns, plates, claws, tails or multiple appendages, limb structure (such as having digitigrade legs) and taxonomic lineage (being descended from reptiles, fish, rodents, marsupials, or a phylum not evolved on Earth, perhaps, instead of primates). Reptilian humanoids are a common concept.
Most of the aliens in television and movies are humanoid, since it is easier for a fictional character to be a disguised human actor. However, there are various methods for presenting non-humanoid characters, for example computer graphics, creative costuming, and puppetry, as seen in shows like Farscape and the new series of Doctor Who. Many aliens and robots often call humans humanoids, although this probably has more to do with translating alien languages, as the word human would appear to be limited to Earth's population only.
Some people find it unlikely to have a universe populated by unrelated creatures that all look human, while others (including some biologists) believe that a species would naturally drift towards bipedalism when achieving sapience as we know it.