Dang this special was so good I cried. Although as beautiful as this song is I decided to play around with the lyrics and experiment what it would sound like if princess bubblegum sang the song. I kinda pictured the two of them sitting on their sofa as bubblegum  gave Marcy her cute version. 
I'll probs redo when I find a cleaner instrumental 
Vocals and Lyrics: AshleyH
Instrumental: https://www.youtube.com/watch?v=nucZg8sKwJI
Vector: https://www.deviantart.com/yorusempai

Lyrics: 
I know we’ll never grow old together 
Cause you’re never grow to me
I’m the pink in your cheeks 
And you're scared
Cause you say you’re a little too soft

But don’t beat yourself Marcy 
Cause even the brightest colors they fade 
I was obsessed with work, always afraid to hurt 
You broke all those barriers 

And you say you’re monster 
Long before you were bit
But you were never a monster
You were only a kid

And We grew up alone 
Holding to the past
But we found each other
And I’m home at last 

We're the perfect fit 
So you better get used to it 

That shirt became my greatest treasure 
The precious gift you gave to me 
Stared at it for hours, the scent that was ours
Though I tried to be strong 

But don’t beat yourself up Marcy
It was me that I was hiding from
Feelings forced down but you were still hanging out 
Scared I wasn’t good enough

You say that your monster 
But I don’t believe it 
Cause if you were a monster
This love I wouldn’t admit 

We may argue and fight
But with you in my life
What’s past is past 
And I’m home at last 

Yes We're the perfect fit 
So you better get used to it 

I know we’ll never grow old together 
Cause you’re never grow to me
I’m the pink in your cheeks 

And I love that 
means your a little bit soft