This gets Sheldon appropriately hot and bothered, until he realizes this purchase means that Amy went to the park without him.
This is when Amy gets the bright idea to let Harry Potter amp things up a bit.
She heads into the bathroom and changes into the Gryffindor school robe she bought during a visit to The Wizarding World of Harry Potter theme park.
As you can probably imagine, an argument at this moment does not make the mood better, but it turns out that Bernadette really is having her baby now, so at least Amy and Sheldon don’t spend the night fighting.