Under Drona's tutelage, the Kauravas and the Pandavas, along with the princes of Hastinapura's allies and vassals, learned weaponry. Arjuna became Drona's favorite and most accomplished pupil; specifically, he became a master in using the bow and the arrow. In a famous incident, Drona deemed that out of all his students, even his own son Ashwatthama, none but Arjuna had the steadfast focus to shoot the eye of a bird on a tree; he was proven right. One day, on being questioned by Ashwatthama; why was Drona being partial to Arjuna, Drona replied Arjuna that he was not being partial to anyone but his favourite was Arjuna. His intention was very clear that he loved Arjuna but didn't ill-treat anyone. He ordered Ashwatthama to gather all of his students including Ashwatthama to assemble at near by lake that evening. they did as Drona told. Drona was taking bath; suddenly a crocodile appeared attacking Drona. Nobody except Arjuna were dare to enter into lake. Arjuna then jumped into lake & began attacking the mighty crocodile with bare hands. Suddenly crocodile disappeared. Drona told everyone that the crocodile was just illusion and created by himself to test all the princes & Ashwatthama. Drona also scolded the rest that they were not ready to save their teacher except Arjuna. Thus Drona proudly declared that Arjuna was his favourite and pet student.