Totally Typecast

She is always:
The caring, usually kind mother who wants to be closer to her kids.

Example:
Elf(2003)

He is always (as everyone is quick to point out):
An awkward teenager/ young adult who tries to win the love of a cute, quirky girl.
Example:
Juno(2007)

She is always:
The slutty, less attractive best friend.
Example:
27 Dresses

She is always:
A high strung Career woman with a slutty, less attractive best friend (one of which was played by Judy Greer, coincidence??)
Example:
(again) 27 dresses(2008)

He is always:
A creepy/ nerdy guy with very few friends.
Example:
Back to the Future(1985)

He is always:
A womanizing creep who ends up learning a valuable lesson about love. The lesson is usually provided by an uptight career woman.
there are quite a few, but I'll go with the most egregious example:
Ghosts of Girlfriends Past(2009)

He is always:
Douchey best friend/ rich guy/ rich best friend. Always douchey.
Example:
Pretty in Pink(1986)