Sri Radha shows Sri Krishna his reflection in a mirror
The Lord’s Reflection

Upon seeing His own reflection in a bejeweled pillar of His Dvaraka palace, Krsna desired to embrace it, saying, ‘Alas, I have never seen such a person before. Who is He? Just by seeing Him I have become eager to embrace Him, exactly like Srimati Radharani.’"

"This is a verse from Srila Rupa Gosvami's Lalita-madhava (8.34)."
Referenced in the Sri Caitanya Caritamrta, Madhya 8.149

"In Rupa Gosvami's Lalita-madhava, it is said, ‘One day Krsna happened to see the shadow of His beautiful form reflected on the jeweled foreground. Upon seeing this bodily reflection, He expressed His feelings: "How wonderful it is that I have never seen such a beautiful form! Although it is My own form, still, like Radharani, I am trying to embrace this form and enjoy celestial bliss."’ This statement shows how Krsna and His shadow reflection are one and the same. There is no difference between Krsna and His shadow reflection, nor between Krsna and His picture. That is the transcendental position of Krsna."
—Bhakti Rasamrita Sindhu \  Nectar of Devotion  #64. Krsna's Exquisite Beauty.