Looks like he puts that finger to use on other occasions too!
Vettel does have a great sense of humour, and seems to enjoy the attention he gets - this definitely makes for a good spokesperson for the sport. And it's highly entertaining for all us fans!
i guess he just managed to stay a bit more of a child than others, which is a good thing as long as you remain focused on what has to be done... looks like he got that done, too.
as for the joke: nice one
He does have a good sense of humour