A simple reason why i don't believe the "Bishop did it" theory
There are many-many theories on how the egg got on the Sulaco, and one of them is Bishop carried them there on company orders, and he was in on it throughout.
Never mind the logistics of this (when did he have the time to carry the egg to the dropsip, where did he hide it on the dropship, how did he retrieve it after being torn in half, and how did he stuck it onto the ceiling of a random corridor? And no, the queen had no time to do this either, but that's another story), I have a simple reason not to believe this theory.
Burke was acting alone. Plain and simple, Burke signed up on this mission to gain millions for himself and no one else. So he went with the marines to gather a specimen all on his own - and he had no support from the company. And that is why he could not reprogram Bishop or plant a special order into him, because for one, that leaves some kind of trail, and he could not afford that, and two, he is no programmer, and could not have involved anyone (like a lab techie guy) to do it.
"Yeah but Bishop is a Company android, so Burke would not have to reprogram him. He automatically does whatever the Company wants."
Except... no one at the company wanted a specimen. The board did not believe Ripley at all. They sent Gorman to be in charge because they couldn't be bothered with some missing colonists. No one saw an opportunity in this for anything - except for Burke. So no, W-Y did not want a specimen, they were skeptical of any aliens even existing in the first place, there was no such order Bishop could have followed.
I rest my case - do I have a flaw in this summary? Let's find out :-)