my lab mix puppy

Question
He is 2 months and 21 days old, He is a lab mix, mixed with what i don't really know but his tail is black, and my guess would be a shepard. But my question is... i went to work this morning and his ears were flopped, by the time i got home they were kinda out to the side and flopped at the tip. Do ears really change shape that fast or is it do to teetheing? Please help , new at this dog stuff.... I also had taken him to the vet yesterday and he got his 6way dhlppc and I thought it was maybe a reaction to the shot?

Answer
I think it is possible erect ears is partly a behavior think once they develop.  If so, a rapid change is quite possible.  I think they can go from down to up fairly quickly, but not in a day.  And yes, sometimes the shots do have a major effect for a day or 2.