Henry Linnell, the sole TMBG child, was born in 1999 to the family of John Linnell. He made a brief (and cute) appearance in Gigantic, during which he informed viewers about the difference between eyes and eyeballs (eyeballs are in your head, eyes are on your face) and discovered the camera viewfinder while eating a bagel sandwich.
He does some speaking for "Letter/Not A Letter" on Here Come The ABCs. On Here Come The 123s, Henry voiced the role of one of the "Sevens" on the song "Seven."