This is my first Tab, so please forgive me if its not 100% correct. feel free to write 
any corrections in a comment!!! :D

(when Ylvis makes the weird sounds, just slide your finger up and down the D string)

Capo on 4th fret

[Ylvis:]
          G
Dog goes woof
          D
Cat goes meow
            Am
Bird goes tweet
                  Em
And mouse goes squeak
          G
Cow goes moo
            D
Frog goes croak
                       Am
And the elephant goes toot
            G
Ducks say quack
             D
And fish go blub
         Am       Em Em Em
And the seal goes ow ow ow
                 G
But there's on sound
              D       (stop)
That no one knows...

WHAT DOES THE FOX SAY?!

Ring-ding-ding-ding-dingeringeding
Gering-ding-ding-dingeringeding
Gering-ding-ding-ding-dingeringeding

WHAT THE FOX SAY?!

W-|a-pa-pa-pa-pa-pa-pow
W-|a-pa-pa-pa-pa-pa-pow
W-|a-pa-pa-pa-pa-pa-pow

WHAT THE FOX SAY?!

Hatee-hatee-hatee-ho
Hatee-hatee-hatee-ho
Hatee-hatee-hatee-ho

WHAT THE FOX SAY?!

Joff-tchoff-tchoffo-tchoffo-tchoff
Tchoff-tchoff-tchoffo-tchoffo-tchoff
Joff-tchoff-tchoffo-tchoffo-tchoff

WHAT THE FOX SAY?!

           G
Big blue eyes
         D
Pointy nose
         Am
Chasing mice
             Em
And digging holes
      G
Tiny paws
        D
Up the hill
     Am                    Em
Suddenly you're standing still

             G
Your fur is red
         D
So beautiful
         Am         Em
Like an angel in disguise
            G
But if you meet
             D
A friendly horse

           Am
Will you communicate by
Mo-o-o-o-orse
Mo-o-o-o-orse
Mo-o-o-o-orse

      D
Will you speak to that
Ho-o-o-o-orse
Ho-o-o-o-orse
Ho-o-o-o-orse

WHAT DOES THE FOX SAY?!

Jacha-chacha-chacha-chow
Chacha-chacha-chacha-chow
Chacha-chacha-chacha-chow

WHAT THE FOX SAY?!

A-hee-ahee-ha-heeee
A-hee-ahee-ha-heeee
A-hee-ahee-ha-heeee

WHAT THE FOX SAY?!
   G
A-woo-oo-oo-oooooooo
   D
Wa-oo-oo-oo-oooooooo

WHAT DOES THE FOX SAY?!

                   G
The secret of the fox
           D
Ancient mystery
                        Am
Somewhere deep in the woods
                 G
I know you're hiding
               D
What is your sound?
              Am
Will we ever know?
                   Em
Will always be a mystery

                 G
What do you saaaaaaaaaay?

                  D
You're my guardian angel
               D
Hiding in the woods

                  G
What is your soooouuuund?

[Fox:]
W-|a-wa-way-do-wub-wid-bid
D-|um-way-do-wa-wa-way-do

[Ylvis:]
              D
Will we ever know?

[Fox:]
Bay-budabud-dum-bam

[Ylvis:]
       G
I want to

[Fox:]
Mama-dum-day-do

[Ylvis:]
              G        (stop)
I want to knooooooow

[Fox:]
Abay-ba-da-bum-bum-bay-dum....