muffet is named after little miss muffet,
snand talks in comic sans font (but pixelated),
doggo literally means to escape detection by a lack of movement,
papyrus talks in papyrus font (but pixelated),
asriel is a combo of toriel and asgore,
toriel sounds like tuTORIEL,
temmie named after tobys friend and main sprite designer
BONUS! ralsei is an ambigram of asriel (ambigram is scrambled letters to make a different word)