You are almost right, Anne! Hanken monos are used 
to promote aspects of a particular anime but in 
this case, they are =never= animated. They are 
hand-inked cels used to produce mass market items 
such as posters, CD/LD covers, ads, and so on. 

The SM hanken mono you saw was probably from one 
of these and not a commercial. 

For more information about hanken monos (with 
examples) and other special cels, please check 
out Brian's very handy page:

http://www.kimonocels.com/Animation/production.htm
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Hanken monos are very expensive because of the 
quality of the image (and art) and because it's 
the original of a mass-produced image. 

I'm sure other people can add more information! 
To the original poster: don't be afraid to ask 
questions but take a look through the cels forum 
archives and I'm sure a lot of questions could be 
answered. 

Best wishes,

Wendy