Too many people know how to do this glitch already, and there are some videos out there that explain the steps to it, so why not share it with you guys?
1: Change into your Spring Bunny.
2: Switch to an underwater den.
3: Quickly change into another water-only animal. While you are doing this, immediately switch to a land den.
4: When you know you've done it right, your bunny will be frozen.
5: Open up the customization menu and change your pattern to any color you like. If you want black flowers, do NOT have a pattern. If you want magenta flowers, DO have a pattern. The color of the two other flowers is based on the color you choose for your pattern.
6: Now refresh, and voila! Your pattern is glitched!