ArianaGrande has been very open about the fact that playing Glinda was her absolute dream role. She wanted the part so badly that she lobbied for it for a full decade before it ever started ...
The extended scene gives a more detailed look at how Elphaba, played by Cynthia Erivo, learns tricks from ArianaGrande's Glinda on how to become popular, including the "toss toss" and more.