after the fight and reconciliation you had with Toriel you can finally move beyond your home and go to other parts to find a way out to the surface, but when you walk calmly a figure a little shorter than you appears in front of you and she just said

Sans: hey, don't you know how to say hello?

she extends her hand to you for a handshake and when you accepted it, a fart sound was heard and it was a half-deflated balloon that she had in her hand. After a while the two of them already introduced themselves and sooner rather than later you noticed the obviousness of their body, with good curves and enviable breasts and she notices your look in them

Sans: meh, sometimes people do that, it doesn't bother me enough

but her flesh was different since with more glances you took you noticed that her legs were blue and a little gelatinous

Sans: hey kiddo, wanna touch it?, I see you too indulged in perverting them in your mind, so it will be funny

this makes you blush immediately which she notices and laughs