...her panties beginning to get thicker.
She grabs them, trying to push them back in shock and disbelief. "No, no, no!" Jen says, feeling them expanding, stretching her pants further and further. She feels them getting heavier and tighter as they press against her pants, before suddenly: "Rip!" and her pants burst to give way to her new underwear.
As the expanding diaper pops out of her pants, the sudden weight gained and the forced distance between her legs makes her trip and fall, landing on a somewhat constable pudding.
Not wanting to thick about it too long, Jen tried to get up, but failed as she just fell again, landing on her hands and knees. The diaper has gotten so thick and puffy, that she is unable to get up, so she can only move while crawling.
But this isn't the worst yet, because...