She had heard his voice on the Network while trying to come to grips with Thom having a Number, but had forgotten until hearing it a second time. While a talking dog itself is not entirely novel, it makes a difference knowing Thom has a Number and that Gizmo is also a part of their family.

Nel lets out a squeal of delight, and then immediately covers her mouth with both hands as she laughs. Bouncing in place without her feet leaving the floor, she looks back to Thom with a huge grin, “This is amazing!” Then she looks right back to Gizmo, “Gizmo, when did you start talking?!”