The Talbot boy, if really their's, would have had blue eyes, Both Talbots had blue eyes, so genetically they could not have produced a child with brown eyes. That would have been a give-away that he was not their blood son.
Heat Wave is less than a week away from being released, yet Beckett is surprised that Castle might write another Nikki Heat novel. If she thought the agreement for Castle shadowing her was for one book, she would have no reason to be calling him when they catch a case as the book is obviously finished.
Perlmutter states that stainless steel crowns are no longer used in the USA so she must have been from an Eastern Europe. This is simply not true. While adults do usually opt for tooth coloured crowns for cosmetic reasons, stainless steel crowns are still used across the world. Particularly when cost, complexity, patient age and patient co-operation for the work are factors.