Added.

I feel you should add "PUZZLE" tag to this Kata because there is guesswork invoved due to the ambiguous example tests.

This may be me solving this later in the evening, but the example test cases imply that it is the last letter of the word that is being repeated twice and then has "k" added.
You may want to consider adding a test case which makes the actual rule more obvious. :)

I laughed very hard about this ine!