what is needed to be a bulldog fan?

A primary teacher starts a new job at a school in Bankstown and, trying to
make a good impression on her first day, explains to her
class that she is a Bulldogs fan.

She asks her students to raise their hands if they, too, are Bulldogs fans
Everyone in the class raises their hand except one little
girl.The teacher looks at the girl with surprise and says:

"Mary, why didn't you raise your hand?"
"Because I'm not a Bulldogs fan," she replied.

The teacher, still shocked, asked:
"Well, if you're not a Bulldogs fan, then who are you a fan of?"

"I'm a Roosters fan, and proud of it," Mary replied.
The teacher could not believe her ears.

"Mary, why are you a Roosters fan?"
Because my mum and dad are from Bondi, and my mum is a Roosters fan and My
dad is a Roosters fan, so I'm a Roosters fan too!"

"Well," said the teacher, in an obviously annoyed tone, "that's no reason
for you to be a Roosters fan, You don't have to be just
like your parents all of the time. What if your mum was a prostitute, your
dad was a drug addict, and your brother was thug and car thief, what
would you be then?

"Then," Mary said, "I'd be a Bulldogs fan."