We already saw that in Natural Born Kissers.>Bart+Lisa
If we keep it innocent, it'd just be them being curious/grossed out by each other's junk.>Marge+Lisa
Bit awkward at first, in the end it would just be friendly mother/daughter bonding (of the non-lewd kind)>Lisa+Homer
Lisa would be grossed out by Homer's junk or else find it funny because she's 8 years old. Homer would be embarrassed a bit.>Bart+Marge
Super awkward. This would be the hardest pairing to write.