Okay here is my theory: Rainbow and Flutter friends from fillyhood always relied on each other. This is shown because everyone in cloudsdale calls Rainbow by Rainbow crash. So Rainbow does the sonic rainboom to protect Flutter from the bullies. When Flutter hits the ground she decides to move to ponyville Rainbow missing her only friend joins the school with Gilda as an attempt to make a new friend or friends however the horrible nickname follows her. On her birthday Rainbow has to celebrate alone as Griffins do not celebrate birthdays. Lonely and bullied she decides she cant take one more person calling her crash and gets in a fight. Being kicked out of school for fighting she decides to take a job as ponyvilles weather maintance pony so she can rejoin her first and so far only friend so she can celebrate her birthday. This is why Rainbow moved to ponyville on her birthday after Fluttershy already moved there and we know this cause otherwise fluttershy would of been included in Rainbows birth/aversary. If you find holes in this let me know.
problem with rainbow dash: How did she come to Ponyville?
in MLP:FiM Canon Discussion
Okay here is my theory: Rainbow and Flutter friends from fillyhood always relied on each other. This is shown because everyone in cloudsdale calls Rainbow by Rainbow crash. So Rainbow does the sonic rainboom to protect Flutter from the bullies. When Flutter hits the ground she decides to move to ponyville Rainbow missing her only friend joins the school with Gilda as an attempt to make a new friend or friends however the horrible nickname follows her. On her birthday Rainbow has to celebrate alone as Griffins do not celebrate birthdays. Lonely and bullied she decides she cant take one more person calling her crash and gets in a fight. Being kicked out of school for fighting she decides to take a job as ponyvilles weather maintance pony so she can rejoin her first and so far only friend so she can celebrate her birthday. This is why Rainbow moved to ponyville on her birthday after Fluttershy already moved there and we know this cause otherwise fluttershy would of been included in Rainbows birth/aversary.
If you find holes in this let me know.
Chaos is the end result of brilliance.