A while ago I chanced across a system extension, "Bugs in the Software" that, when placed in the extensions folder of a Macintosh system folder, changed the normal 'pointer' cursor to one of several insects. I have used that extension for quite a while with no problems (on a Powerbook Duo 230 running system 7.5.5 and 7.6.1 and more recently a Powerbook 2400c running 8.1, 8.5, and 8.6).
I have modified that extension to add a turtle pointer. The extension is the same - I created the cursor in Resedit and used that program to alter the icons associated with the extension. It has run okay on all the systems I've used (7.5.5 to 8.6). If anyone finds an incompatibility, please let me know. The 'hotspot' for clicking is at the tip of the turtle's nose, by the way.
I have made two versions, a color version and a black and white version. The color version has both black and white and color information - if you change the resolution of your monitor to B&W, the cursor will switch to B&W, but will remain in color for 8 bit or higher color depths. The B&W version will not give a color cursor at any of the color depths, so if you find the color version too distracting, you can use that version.
The two versions are downloadable below. They are saved as binhexed, self-expanding Stuffit files in a single folder. The inspiration for this work was Jeff Dawson, who made Turtle Windows95 cursors. Macintoshes use a 16x16 bit cursor, much smaller than the 25x25 turtle he constructed, so I had to create one from scratch. This extension also will only change the pointer cursor - all others should be unaffected, as will any programs that use their own built-in cursor, rather than the system cursors.
To change your cursor to a turtle, download the folder to your computer (drag to the desktop from your web browser window or click on the link). Depending on how you have your web browser configured, it may automatically decode the file, or it may leave it as a "TCurs.hqx". If it does not decode it, then use Stuffit Expander to do so. If the file is downloaded and saved as "Tcurs.sea", then double-click on the file and it should extract itself. Open the "Turtle Cursors" folder, take the desired extension and place it in your System folder in the Extensions folder. Restart your Macintosh. The pointer cursor should change to a turtle after the Mac has restarted. Enjoy!