Poor Marty. In this story, there is no magic. There is no wand waving here. In stories with magic, when someone changes a pumpkin into a carriage or mice into horses, no one worries about the change in mass. “It’s magic,” works as an explanation for such questions. In this story, there are physical transformations, and I need to come up with a hint of the how for each one. So my mermaids and werewolves don’t magically transform in a cloud of pixy dust. Everything happens because of technology and/or laws of nature.
So, in Marty’s new state (which isn’t a total surprise if you’ve seen the cover of this comic) his frame is quite a bit thinner. Naturally, there would have to be a change in mass and density, and in this case, that change sounds like, “huerchgle” and “sploosh” as it leaves his body and hits the toilet water. I know the sound effects are pretty gross, but drawing someone evacuating that much liquid would have been slightly grosser. Trust me, things get a lot less disgusting on the next page, so read on!