I've never tried to speak Korean but I was not aware it was such a difficult language to learn that you would have to have your tongue surgically lengthened.  However, a 19 year old British girl did just that.

She says that she spoke the language and sounded "foreign".  But since the surgery she is able to pronounce words that, before the surgery, she was not able to pronounce.

The surgery is called a lingual frenectomy.  It's actually only about a 15 minute procedure and has little recovery time.  So what is a lingual frenectomy?  That little piece of tissue under your tongue that connects it to your lower mouth is snipped to allow the tongue more movement.

I'm guessing that's what Gene Simmons did years ago.  Not really but can you image if he did how long his tongue would be?

 
Here's a video of a child having the procedure done by laser to correct a very short tongue. Obviously this was done on someone who needed the surgery for medical reasons not just to speak a foreign language better. I'm a very squeamish person and I watched it so it's not bad.