Mission 2 to Destroy All Humans is a very short and easy mission. It's basically there to simply serve as an extended tutorial by introducing the Holo-Bob, a disguise-based power that will become very important throughout your time playing the campaign.
There is only one optional objective in this mission, but while it's simple to do, you can easily miss it if you're not careful.
Shortly after getting your first Holo-Bob, you'll arrive at the salon. You will be ordered to scan the minds of various humans. All you're supposed to do here is scan Miss Rockwell. You can find her in the giant tent, the entrance to which will be on the other side of the fairground when you enter. Enter the tent with your Holo-Bob active (scanning the human brain will refresh the timer) and scan the woman in the red swimsuit. Once his thoughts are done speaking, you'll enter a quick cutscene with Orthopox where he tells you he wants you to take her back to the saucer.
When you return to the game, you have the option of brainwashing him to follow you to the saucer. You will also notice the optional objective of escorting him there as the mayor is active. Before brainwashing him, come out of the tent and look to your left where you'll find the mayor giving a speech on a stage. You have to make it into a Holo-Bob, but doing it in the open will alert everyone to your presence. Walk to the back of the stage and start taking a new Holo-Bob from him. When you take his image, the mayor will become transparent, which does not alert the crowd. Go back to the tent and brainwash Miss Rockwell now.
Now Miss Rockwell will follow you wherever you walk. All you have to do is just escort her out of the fair and to your saucer. If you walk too far in front of her, she will stay still until you come back to her, so make sure you walk slowly enough to keep her close. If your Holo-Bob starts to time out, just scan his or someone else's brain and he'll cool off. Walk towards the saucer easily and you will reach the objective and immediately have the chance to destroy the fair before completing the mission.
