You will notice that young Squirrelly Q isn't shown in full at the beginning of the book.  This is intentional since the reader is on the journey with the characters to solve the mystery of his identity.  When he meets Maximus, only his swirly tail is visible to the reader.  The reader is primarily seeing what Squirrelly Q himself sees (like when he meets Mr. E and Sherlock).  The reader sees small glimpses of Squirrelly Q in the black smoke, getting clean in the fountain, and talking this friends by the castle, but must wait until the last page when his identity is revealed and he is shown in his entirety.  By the time he meets his mother at the end, he has grown hair and features that make him easily identifiable as a squirrel. And since his mom has a "Q" to her tail just like his, there is no mistaking their relation to each other!