Characters: Bruce, Tony, Natasha, JARVIS, (other Avengers in limited capacities)
Warnings: Implied child abuse/neglect. De-aging.
Disclaimer: Not mine, as nice as it would be
Tony is suddenly a quiet, wary five year old boy. The rest of the team are less than completely sure about what to do about that.
(This was posted on AO3 some time ago, I'm just cross-posting here for completeness sake)
( Bruce Banner was a physicist, and physics had quite a lot to say about time travel. Unfortunately, most of those things were best filed under the heading "it's impossible, and here's why", which he found quite infuriating given the very real evidence to the contrary sitting in the next room. )