A pony is not born with a Cutie Mark, they appear when a pony discovers their purpose in life, or their special hidden talent. Apple Bloom is among the last in her class to get hers though, and feeling left out she does everything she can to earn it before an upcoming party.
Season 1 Episode 12 of My Little Pony: Friendship is Magic resulted in a 0.00 rating in the 18-49 demographic.
"Get your muzzle out of those books and make some friends!" That's what Princess Celestia tells Twilight Sparkle. She may be the smartest unicorn in Equestria, but Twilight Sparkle gets an "incomplete" in friendship. There's more to life than learning magic, after all - so she goes to Ponyville on a mission to make friends. There she meets five special ponies who take her on exciting adventures and teach her the most powerful magic of all... the magic of friendship!