Multiple character encodings within a single database/table?

If I have the C locale, can I have multiple character encodings within:
1.  A single database?
2.  A single table?

More specifically, I would like to be able to have Unicode columns and
ASCII text columns within the same table.  Is this possible?  If so, how
do I achieve it?

It was not clear to me from:
http://www.postgresql.org/docs/current/static/multibyte.html

It seems to me from this statement:
"It can be overridden when you create a database, so you can have
multiple databases each with a different character set."
That it may be database wide, but I am not sure that it is not possible
to have both ordinary char and Unicode in the same table.

Possible or not?