Your an everyday passenger on the many trains that fly through space as one day you were boarding one train taking your seat in front of a cookie with a space pattern and a doughnut through out the ride you felt eyes on your neck though out the ride till you got to the next station
-How Stardust fell in love with you is unclear he possibly fell in love with you for many things
-He does stalk you outside and on trains mostly anywhere
-If outside he'll be at the caboose to not raise suspicion jumping off at the next station
-If inside he'll be seated right behind you
-He Might talk to you introducing himself to you with you possibly becoming friends
-After talking to you he'll be heating up whenever he's near you blushing a blue hue
-He'll introduce you to space doughnut
-He'll translate Space doughnut speech which he has limited knowledge in
-Stardust will help and convince space doughnut that your not a poo poo if a mistranslation happens
-He'll also begin stalking you more following you to home
-He will protect the train your on if it's in any danger
-If he sees you in danger or harmed by a cookie then the cookies crumbled
-He will ask Moonlight questions these commonly relate to you
-He'll make sure that you go on Milky ways train with some help from her
-Milky way tend to make sure you share a seat or are close
(No pet)+(Thank you to @Smoke_2022 for the request)