We are both constantly penetrating your mum.
Because she's always drinking from the coup de Grace. (This was my sister's favourite joke when we were kids. Once our mum flipped out on a long car journey because she told it too many times).
Because of their Crystal Balls EDIT: I'm not sure if anyone's posted this before my mum's sister emailed her from across the globe.(New Zealand) I laughed so hard I thought I'd put it here. Credit goes to my Mum's sister though.
Because they make up an awful lot of stuff. EDIT: Because I forgot about neutrinos.
We're both constantly penetrating your mom
They have the ability to penetrate both holes at the same time. explanation(http://en.m.wikipedia.org/wiki/Double-slitexperiment)
We're always penetrating your mom
