This is my first tab. I think it sounds pretty good...

Intro:
G D Am C

G
Peter is smart 
                         D
He knows each European country by heart
                          Am
He likes to sit under an apple tree in his yard
                 C
And wait for an apple to fall
        G
When Peter is nine
                           D
His teacher tells him the planet is dying
                          Am
Someone needed to put an end to it all
        C
And so Peter goes home and tells his mum

Chorus:
     G                  D                 Am    C
I'm going out into the world to save the planet
    G               D                Am    C
And I ain't coming back until she's saved
     G           D                 Am       C
I'm going off to see the king and parliament
     G                     D           Am
If they don't help me I'll do it by myself
    C
I don't wanna be
G           D         Am         C
Da da dum...

(SAME CHORDS THROUGHOUT)

Peter is young
He tries to talk but nobody listens to him
Everybody's busy living and dying
Not knowing what's going on
But look at the little boy who

Chorus:
Went out into the world to save our planet
And he ain't coming back until she's saved
He's going off to see the king and parliament
But they just shook their heads and walked away
Singing
Da da dum...
Da da dum...
Well I'm going out into the world to save our planet
And I ain't coming back until she's saved
I'm following the footsteps our young Peter made
And everybody is welcome to join
Sing with me
Da da dum...
Da da dum...
Da da dum...

*Hold C to end*