I say this all the time about DD (6 months) and I've been doing it pretty much since she was born.
When she first started oooohing and aaaaahing at us when she was around 5 weeks old I told people she had started talking.
People who go on about how advanced their children are ridiculous so it makes me laugh to make really preposterous claims for my baby.
It's getting less amusing now that she actually does things (well OK, one thing. She can roll now, I believe quite a long time after the books indicated she might start), but I found it really amusing to go on about how advanced she was when she was a newborn unable to hold up her own head.
DH likes to do the opposite. He'll say things to her like "my goodness are you STILL pooing your pants?" or "OMG you're such a BABY!"