One of the many companies Aardman Animations (the studio behind Wallace & Gromit and Creature Comforts) have made adverts for is LEGO. What is uploaded on YouTube by the Hall of Advertising channel is one advert done for Train...
And one very impressive advert done for Pirates...
But also, my Creating 3-D Animation book mentions a spaceman advert Aardman made that was similar to the Pirates one. I looked it up and yes, I found a Space advert with the same construction characters (2:30):
But I've also seen listed in an interview a mention of producing advertising for LEGO Star Wars. This interview came out before Chicken Run and LEGO Star Wars came out in 1999 so it must have been in the franchises early years.
http://www.telepathy.co.uk/aardman/culture/faqs.html
Does anyone know of some early LEGO Star Wars advert with stop-motion in it?