'The Little Couple' -- Everybody Poops ... Especially Our New Son!

Jennifer Arnold and Bill Klein -- stars of TLC's hit "The Little Couple" -- just adopted the cutest little boy from China ... and like any sized parents, they have quickly learned ... TODDLERS POOP A LOT.

Our photog spoke to Jen and Bill on the streets of NYC as they walked hand in hand with the newest addition to their family, 3-year-old William, who was also born with a form of dwarfism.

It's clear from the video the new parents -- who struggled for years to have a kid -- are excited to learn the tricks of the trade.