So, the shock ending of 'How a B.E.M. (*) ate your mother' , was that whilst the mother was eaten by a B.E.M. she was herself a B.E.M. and.... wait for it... ... the B.E.M. that ate her was her daughter, who ate her way out of her womb, that being the life-cycle of their species.
A shock ending, but I am kicking myself for not seeing it coming.