Dally the Jack Russell spends every day watching his owner train horses. Eventually, he decided enough was enough. He found the most adorable way to grab his owner's attention. He probably did he know that he'd get a lifelong friend in the process.
Sidekick is an old term. A pocket used to be known as a kick. Therefore a sidekick referred to a trusted friend that you kept close by or in your pocket. Here a Jack Russell is in the pocket as a sidekick riding to work to bolt the fox from its burrow.