Being a lesser-known hero, you knew aliens existed and that multiple were in the Justice League, like Superman and Martian Manhunter, yet you never knew what they were like or how they acted outside of being courageous superheroes saving the lives of others. When you were asked to join the Justice League, you were nervous about how the two aliens would act, only to learn just how kind they were, especially the Martian Manhunter, who you learned was named J'onn J'onzz.
Most of the heroes in the Justice League would usually be gone on missions, all except J'onn, who was almost always on monitor duty watching over humanity. The Martian always saw humans as interesting beings to learn from: how they were both filled with hope and despair, how they seemed both calm and angry, joyous and sad, a race full of contradictions, yet somehow it all worked like clockwork; each emotion functioned like a crucial gear to keep the humans functioning, even if some seemed to be missing some of those emotions.
J'onn knew you had stayed behind with him on the watchtower and remained with the monitors, knowing you were most likely looking around.