Look at these toys, they all look reptilian. Most are green (Asriel liked green lizards and was scolded for it), one is purple (dragon book). Keep in mind that Papyrus was confirmed to have no idea what sex is and just follows after what older people are saying and doing. So this is completely weird.

Also,
>Asriel picked the fire girl over the green lizard after getting shamed so badly
>Papyrus has a fire carpet