Pass the Mustard... or Ketchup?

So my fiance hates ketchup and eats mustard on everything. This April fools day I am going to play a prank on her. One she won't be expecting.

I do apologize in advance for the small pictures. This is my first instructable and I used my cell phone to take pictures.

First thing you need to do is remove the cap from the mustard.

Stick the corner of a sandwich bag down in the mustard jar.

Fill the bag with ketchup

Replace cap to mustard.

Cut excess bag once you have the cap back on.

Have a camera so you can catch their reaction once they go to apply mustard and ketchup comes out.