Relayed from my tumblr post,
I 've made this comic after finding a most disturbingly hilarious GIF spodiddly.tumblr.com/post/6063923336/spocks-tongue 
From that my headcanon was that Vulcans have elongated tongues during sexual arousing activites.

(Yes the comic is there also, but I wanted to post it here as well)
( Yeah, I know I'm weird... )