Contrary to popular belief, little Frodo Baggins, the youngest (and teeniest) Dwobbit of the Line of Durin was NOT grown in a cabbage patch.
"It was among Bilbo's prized tomatoes, the cutest, most adorable wee thing and thankfully, Mahal heard my prayers and blessed him with Bilbo's curls and his nose," says Thorin with the most besotted grin on his face, whilst carrying Frodo against his chest, wrapped in a sling.
Bilbo is too busy hiding his hysterical laughter because the look on Thranduil Elven-king's face was just.... epic. There is no help or hope of common sense coming from the Hobbit side.
Frodo was still too young to say anything but he did help his Uncle Thorin... er.... Adad... by flashing that same identical Thousand Watt Grin at the Elves of the Greenwood.
Yeah, they didn't know what hit them.
Frodo, much like his older cousin Kili, grew up knowing how much of a walnut his Uncle Thorin was.
"But that's why we love him, my lad," Uncle Bilbo tells him, after telling Frodo the Epic Tale of How Uncle Thorin Finally Used His Proper Words and Properly Courted Uncle Bilbo.
The Incident About Hobbit Potato Babies was just the beginning of a long and fruitful partnership of mischief, jokes, pranks and mayhem between Frodo Baggins and his Ridiculous Walnut of a Dwarf Uncle.
The Hobbit Uncle will never admit to Aiding and Abetting said Mischief. Secret Weapon and all that.
Thorin toting about baby Frodo (with his stuffed plushy dragon from Uncle Bofur) soon became a common sight around Erebor and Dale. The Menfolk tended to do double takes. The Dwarves who had already seen their King behave just like this when Princes Fili and Kili were wee pebbles just smiled and waved at the newest member of the royal family.