History
The Avenger Four was a time machine developed by A.I.M. (Avenger Idea Mechanics), meant to be more precise and energy-efficient than Time Platform.
When the machine was first tested, it short-circuited, because Tippy Toe had mixed up some color wiring.[1] This accident caused a disturbance in the timespace that allowed the Avengers from the Year 20XX to open a hole into the present, in other words, their past.[2]