Err... sort of. I think I was watching vsauce recently and heard about this jellyfish called Turritopsis that, after reaching sexual maturity, can regress it's body back into infancy.
Now, obviously, a jellyfish has a much simpler cellular makeup than a human, and I'd hardly rather be a jellyfish than a human. Additionally it isn't a 'baby' in the same way a human would be; more like a larva.
Anyway, I just thought the idea of an animal that turns itself back into a 'baby' would interest the community... Or something. I just thought it was cool!