I hate that kind of interspecies hybridization. It's senseless, stupid and a cheap way to make aliens more likeable relate-able while keeping special effects budget low.
For example on skyline the invasion, which is an awful movie, the aliens are invincible monsters capable of rebuilding themselves from a nuclear blast, in short they are magic, and no, is not a case of sufficient technology is confused with magic, it is stupid magic and plot armour. Anyway, they harvest humans for their brains? WTF? Why would they need wet ware like that if they are capable of traversing the vast distances of space they are more than capable of building chips, or hey, making clones of a perfect brain or use the same magic they employ to rebuild from a nuclear explosion or something.
I keep imagining the robots failing to function out of a million ways because different brain diseases, imperfections and what not. And finally the protagonist (no spoilers because no one saw or care about that excuse of a movie) is able to steal the machine his brain is because of love. I have news, he's not the only one that loves his wife/girlfriend with burning passion, heck, the douche is not even a great example of it. So ,how long before literally millions of other humans do this too and the aliens met an ironic and premature end?
Biology on realistic basis should be really incompatible and even so different that you might have difficulties recognizing alien life the first time you see it.