The first and last are purposely sung in that voice. It's not even Pinkie's voice...idk what it is to be honest...but enjoy it nevertheless!!

Thanks to to creators of these songs, which you can find through Sherclop Pones' channel :)

I love FiW, it's hilarious! And the songs can be so messed up yet so fun to sing xD
Oh, and I am aware of the mistakes, I just got lazy to resing them ^^; Especially the Twilight one, because my parents would have most likely questioned my sanity.