ElitePets is a highly customisable inventory pets plugin. Using this plugin you can create your own pets with custom effects.
Almost everything is configurable all the way down to what noise the pets make
You can even create your own effects using the easy to use developer api, however the plugin already comes with 14+ custom effects and that number will only increase with how many updates are done.
The API for this plugin is very extensive and allows you to control a lot of features about this plugin. You can also create your own custom effects that work with the pet system.