The lyrics goes :
"bla bla bla bla pookie. Ferme la porte, t'as la pookie dans le side."
"blabla" is an onomatopea for the fact of speaking.
"Ferme la porte, t'as la pookie dans le side"
Close the door, you have the pookie in the side.
This means that you have to close the door, because the pookie is listening what you're saying from outside the room and he or she will tell it to everybody.