Some lore stuff about what exactly the creature that has been given to Granny is
Sawdust is what, in my universe, is known as a Bitty. Bitties are the baby form of stick figures. They have a very specific growth cycle to get to looking like stick figures like Purple and Agent.
When a stick figure is born they look like a cross between a few different animals and the exact animal depends on the stick, but there are a few common features. They are always quadrupedal, they have a tail, and are born with their eyes and ears closed. Most bitties are fluffy and look similar to either a kitten or puppy, but some are known to be feathered like a baby bird or scaled like a lizard. It is possible, but extremely rare, for bitties to be born with hooves instead of paws. This is often seen as a birth defect though and can lead to serious hand related health issues when they grow older.
For examples of the mixing of creatures, if Red were turned into a bitty he would be very cat like with claws and whiskers, but he would also have tiny tusks like a boar. Meanwhile if Purple was she would look more like a puppy but with a carapace similar to a bug. Another example would be my Agent was a very dog like bitty with a tail and paws similar to a lemur while Primal actual had a build similar to a mule with a cat like tail, though she did not have hooves.
Bitties will stay in this stage until they are roughly 3 to 5 years old when they start going into what is referred to as the "raptor stage" where they start to rear up on their hind legs more often than not but their bones haven't finished shifting to where they can stand up fully without any trouble. This is often called the Mischief Phase as this is when they can finally reach the counters and tables with their front paws. They usually shed their baby fur or feathers at this point as well.
By roughly 7 to 8, they are able to fully stand up all day without dropping down onto all fours and are no longer considered a bitty, but they are still a child. Sticks do not reach Legal Adult until they are 18. Also roughly 6 months to a year after they fully transition to two legs their tail will fall off. This is completely painless and treated similar to when a human looses their first baby tooth.
Another important fact: Bitties are usually born in litters of 3 to 6. It is not advised for them to be raised solo but it's also not extremely uncommon. It's mostly a problem of socialization, which can be negated by lots of play dates with other bitties