19 September 2008, 15:48 | Updated: 30 March 2016, 13:50
Katy's hit, I Kissed A Girl has inspired a number of parodies on YouTube.
We've picked out some of our favourites for your... ahem... viewing 'pleasure'.
I Kissed An Elderly Girl
The taste of her denture cream... nice!
I Kissed A Squirrel
The taste of her peanut chap stick... we dare you to try and sit through the whole thing as it's really annoying!
I Kissed A Cat
And the animal theme continues... some people have far too much time on their hands!