
...based on the NUMBER of mailboxes and
given typical urban population density...
The Big Bang Theory Season 2, Episode 15

There are a NUMBER of acceptable answers.
For example, C, near-Earth transport.
The Big Bang Theory Season 2, Episode 13

Image NUMBER one: Frenchman
on bicycle carrying baguettes.
The Big Bang Theory Season 7, Episode 5

Number one, and of course, NUMBER two.
The Big Bang Theory Season 2, Episode 22

Judging by my e-mail, a NUMBER of prisoners
at the Michigan State Penitentiary found it.
The Big Bang Theory Season 1, Episode 17