Wrapping a soft cloth around a dog's leg does not make it a cast.
The letter that Jonathan reads in the penultimate scene ends with "I'll love you forever" on paper, yet the actress' voice-over simply reads: "I love you".
Since Jonathan is in human form and living with a rich lady friend, it's very odd that he's been wearing the same clothes for 2 months.
It is not explained what became of the little rescue dog.