jee
I've found

Le Clever Animation JavaMouseOver Button!
This Java applet was crafted by Dave Griffiths and modified by myself to mimick the mouseOver function of JavaScripting...


How to implement it:
Required are an animation "strip": gif or jpg - and, residing in the same directory animBtn.class

The applet can take the following PARAMETERS:
fps (Default 10) - Number of frames per second.
target (Default _top) - Target frame.
step1, step2, step3 (Default 1 in each case)
  These values set the number of frames in each of the three animations.
Step1: is when the mouse is not over the button,
Step2: when it is over the button, &
Step3: when the mouse is clicked.
  The frames of all the animations are stored in a single GIF or JPG image:
images (Default "anim.jpg") - The image file that stores all of the frames in-line, left to right. The images used for the buttons on this page are:

         

(These strips may hold a complete animation if desired.)

sound (Default N/A) - The .au sound file if desired.

The above is a brief explanation of the applet. I have prepared a FAQ

Please visit Davids' site
http://pw1.netcom.com/~jcheves/mousjava.html o implement it? You need 3 elements 1st: an animation "strip": gif or jpg. (Your 2 "in"-"out" images combined into one image) What is the "image strip"? How do I create it? If you have a 10x10 gif/jpg, your strip will be 20x10, or twice as wide. Insert "off" first, and "on" second. (or You can add as many images as you want to create a full animation - similar to creating an animated gif) The applet "reads" the strip in a similar manner... 1st imagess Number of images in animation Image on click You will need to change the width & height to match your image.. (Line 1) and the Name of your image "strip". (Line 2) If you need one, the URL value.. (Line 6) Frame Target -- default: _top... (Line 7) & if you want sound, add it! Otherwise remove. (Line 8) One final note! My tests don't work with Explorer. On my machine IE returns errors when testing "local" java apps, so you might have to upload to your server and test whilst online. I can test any applet with Netscape by dragging or typing the local file, so I suggest you use this for development...!!