Clearly adoption or Maureen cheated on John both options are equally possible. I imagine if John even dared to question if that was his child as he's not black Maureen would of beat and belittled him so he remained silent and raised her as his own.

@Oldnewbie said:

Waiting for an explanation as to why Judy is black. Or are we as modern PC audiences just to assume white families can have black children? But like the recent "Fantastic 4" where Johnny Storm was black... it just is a elephant in the room to anyone knowing the source.

Everyone is a robot!

Er, sorry, wrong show :)+

Judy said in a later episode that her current parents got together after she was born.