It appears that Google changes it’s Google Doodle just for you on your birthday, assuming that Google knows what your birthday is. While I like it, the only potential problem I see is that it effectively hides what the “real” doodle is for the day. For instance, today’s actual doodle was the following:
In other words, had I not used an incognito window to see what the doodle actually was for the day, I would have never known about Emmy Noether. Though to be honest, I never really pay attention unless it’s something cool and interactive like PAC-MAN.