These lyrics are almost the same as what Musicman posted, but there are a few corrections.
Source: A Pretty Girl Is Like a Melody and other Favorite Song Hits, 1918-1919 (David A. Jasen, Dover Publications, 1997)

K-K-K-KATY
(Geoffrey O'Hara)

Jimmy was a soldier brave and bold.
Katy was a maid with hair of gold.
Like an act of fate,
Kate was standing at the gate
Watching all the boys on dress parade.
Jimmy with the girls was just a gawk,
Stuttered every time he tried to talk.
Still that night at eight,
He was there at Katy's gate,
Stuttering to her this lovesick cry:

CHORUS: K-K-K-Katy, beautiful Katy,
You're the only g-g-g-girl that I adore.
When the m-m-m-moon shines over the cowshed,
I'll be waiting at the k-k-k-kitchen door.

No one ever looked so nice and neat.
No one could be just as cute and sweet.
That's what Jimmy thought,
When the wedding ring he bought.
Now he's off to France the foe to meet.
Jimmy thought he'd like to take chance,
See if he could make the Kaiser dance.
Stepping to a tune,
All about the silv'ry moon,
This is what they hear in far off France: CHORUS

Words and music by Geoffrey O'Hara, Army song Leader (born in Chatham, Ontario, in 1882)
"Lovingly dedicated to K-K-K-Katy Richardson, who inspired this song."
copyright 1918, by Leo Feist, Inc.

The sheet music bills the song as "The Sensational Stammering Song Success Sung by the Soldiers and Sailors."
The Great Song Thesaurus says French lyrics for this song were written by A. Bollaert.
I'd love to see the French version.