This is easily deductable, although can only be solved once the birth has taken place.
If the child is ruggedly handsome and looks somewhat like teen spirit, then Idle should be paying child support for the next 18 years. If, however, the baby comes out glowing red and producing enough watts of light to power a small emu farm, then you're looking at Bobo. If the child were a sprog of FIG's, it may very well be orange in nature and have hilariously well placed hair. SO ON AND SO FORTH.
However, I'd wager my money on it being an amalgamation of all present. You can feel it just by looking at those pictures, some horribly crime against nature has no doubt been perpetrated.