The Winchesters by Deadmockingbirds

The Winchesters - Deadmockingbirds

4.5 stars. A lengthy yet entertaining kidfic in which Dean is returned to childhood when he is spiked with the drug Modlenol. Sam and Cas Winchester who practise a domestic discipline lifestyle adopt the 'moddler' as their son. Young Dean is highly cute in this, oftentimes thinking with his adult brain while trapped in a kid's body.

"Fine. I'll go with you two."
Sam smiles wide at Cas like Cas just bought him a pony. And I guess he kinda did.
And that fucking pony is me.

Source: http://archiveofourown.org/works/3160409?view_full_work=true