Any girl that qualifies as such.
Girl Must meet the following qualifications:
3. A Great Person
4. A Great Girlfriend
If you see a B.P.E. on the street, you'd best chase her down, because if you miss your chance with her you'll regret it.
B.P.E.'s tend to make guys lives amazing, and in general, B.P.E.'s get attached to dogs as well.