I love Team Starkid, and my favorite Starkid show currently is TGWDLM. And I have noticed a crap ton of foreshadowing and symbolism and such. So this is basically just rants and essays on TGWDLM because I'm a nerd.
Major spoiler warning.

Meanings Behind Songs
The Guy Who Didn't Like Musicals
So basically the introduction. But at the beginning of the play, Emma is here. In fact, everyone except Paul is here. This implies the end has already happened. Everyone is already dead.
Lah Dee Dah Dah Day
This gives us some foreshadowing which I'll cover in the next section.
What Do you Want Paul
Same here.
Cup of Roasted Coffee
Mostly comedy, and gave us an intro to Cup if Poisoned Coffee.
Cup of Poisoned Coffee
Oof. The major conflict begins. THINK ABOUT THE IMPLICATIONS.
Show Me Your Hands
Mostly comedy as well as bringing Sam into the picture.
Tied Up My Heart
Uh oh, Charlotte is manipulated. More foreshadowing.
Join Us and Die
I am fairly sure this song just exists to show off Jaimie Lyn's voice because DANG.
Not Your Seed
To give us some sadness and empathy.
Show Stopping Number
Comedy as well as more foreshadowing.
America Is Great Again
Ooh okay so this song is NOT FUNNY and every time I watch TGWDLM and I get here and people begin laughing it makes me mad. This song is terrifying if you get the meaning. Yes it's a reference to Trump. But it's scarier than that in so many ways. It's the idea that the aliens want to unite us, kind of. "America is Great Again." THEYRE SAYING THEY ALREADY WON. They killed the military. What hope do we have left?
Let It Out
I love this song. I love Paul's conflict, I love how he begins choking and just falls to the ground. I love the pained "God help me out!" Towards the end. I love it all. It's amazing.
Inevitable
Wow. No words. Very scary ending.

Theory on The Aliens

Yes hello so basically every musical has a character who desperately wants something. No matter what, every musical does. This is where we get to all that foreshadowing.

In Lah Dee Dah Dah Day, everyone singing wants something. Green peace Girl wants to save the planet. Homeless man wants to kill everyone. During What Do You Want Paul, Mr Davidson wants.... something.

Well then he says "I want you to want Paul." We will come back to this.

After Not Your Seed, McNamara asks Paul if he would like to be more than friends with Emma. Paul says he wants there to be. McNamara then points his gun at Paul, which is played off as comedy.

Basically, Paul spends the whole musical not really wanting anything until that moment. Since he wants nothing, the musical plot can't advance through him. Notice every character who dies wanted something before they died.

My theory is that the aliens latch onto their wants and desires, which is how they enter. It's also hinted at during Let It Out when they say "We got everything we wanted."

Meaning Paul was killed by caring about Emma. So why did she survive till the end? Honestly, she didn't know what she wanted. Except that she didn't want to die in Hatchetfield.

She didn't. She died in Clivesdale.