Clicking one of the Living Shadows during Death Marks animation used to display Akali's portrait. This could only be done while spectating in slow motion as his shadows in an actual game were just simply too fast to be clicked on. It was removed after the new HUD came in 2015 and replaced the old one.
Zed and his enemy counterpart can theoretically increase their AD infinitely with Reaper of Shadows by alternating killing each other.
Zed used to gain the 'Law of Inverse Ninja Strength' hidden passive ("This unit is a flippin' ninja!", "Ninjas are more effective when they work alone. For every Ninja on your team beyond yourself, you lose 1 health.") when he, Akali, Kennen, and/or Shen found themselves on the same team (removed during Preseason 4 for unknown reasons).
Zed and Shen trained together in the Kinkou Order, lead by the latter's father Kusho. Both students saw each other as rivals, but Shenrespected Zed, seeing him as a brother and even being a bit jealous of him (Kusho was less strict towards Zed)
Zed, Shen, and Kusho worked to discover and capture Khada Jhin for his brutal murders. All three of them were severely traumatized during the investigation and, when they finally caught the 'Golden Demon', Kusho spared his life. Zed couldn't believe such a monster was offered mercy, finding himself question his master's teachings to the point of heavily resenting him and ultimately murdering him.
In spite of Zed's and Shen's animosity, Zed sought out Shen and to inform him about Jhin's release, in order to stop him together.
Zed's resentment towards Kusho led him to delve into the shadow arts, founding the Order of Shadow and slaughtering the Kinkou while taking up residence in their old monastery. He seeks to abolish the old ways of balance while spreading his 'no restraint' philosophy, murdering any ninja who refuses to learn.
It is implied Zed had a 'favorite student' suspected to be Akali (might explain why she wants him dead while Shen thinks there might be another way and Kennen believes he is not beyond redemption)