Yes there is a password for it.
The password for Lucario was made available in the Weekly Famitsu issue released December 22, 2011.--Bulbapedia
For English, French, German, Italian, Spanish
The password for this promotion came with specially marked copies of Pokémon Black and White available in participating American Target stores starting January 15. Copies with the password were limited.--Bulbapedia
Lucario is the last pokemon to look.