My favorite headcanon about Lance that he’ll flirt with anything that walks and come up with lines on the spot but once someone flirts with him, he just shuts down:
Prince Lotor: Has anyone ever said you have the most beautiful eyes in the world?
Allura: Excuse me, I am-
Prince Lotor: No, not you. Him. *winks at Lance* How you doing?
Lance: Error 404