WHAT romantic spark??? They were DRUNK -BLACKOUT drunk, at least in Peter's case - and Wacker has flatly stated that Michelle has NEVER liked or respected Peter in any way whatsoever. Even with alcohol, this story has given NO REASON WHATSOEVER for them to have sex, beyond The Plot Says So, which means that Michelle is either a character who was MEANT to be portrayed as having sex with men whom she doesn't like or respect, or else the writers' ideas about both women and relationships are defined purely by shitty sitcoms, in which The Bitch magically falls in love with The Loser for no other reason than "It's funny" (even though it isn't).