Ok first of all this is my Au btw and second is when Ink tp or going to his splash of ink with someone, They get motion sickness bc if you go to inks splash of ink you'll only see colorful colors going crazy and it gives you hallucinations. Also dream and blue hate when ink does that xD
Wouldn't it also be Killer, Horror, Dust, Error's bday too since they all originated directly from a classic sans? Like.....if it were Night and Dream, whose origins were more based off MLP lore then UT lore, or Blue whose more based off Papyrus then Sans then yea I get not celebrating their bdays