Tuck Johnson was abandoned some time during development prior to the Andale-based unmarked quest Our Little Secret being completed. Little remains implemented with regards to the non-player character, but remaining AI packages and code snippets lend clues as to his intended role within Andale. The character was to be based primarily out of his house (location not specified) and would proceed about a normal routine. It is not clear if any special conversations were to be available between him and the Lone Wanderer, but remaining dialog and conversations in the associated packages for Andale residents have him responding to the Lone Wanderer in a friendly, welcoming manner.
Curiously, though the character is placed in the game's files as an adult, a non-player character to non-player character conversation snippet suggests that Tuck was intended to be a child. Specifically, Bill Wilson's lines spoken to Junior Smith ("How's it going, sport," etc.) can be directed either at Junior or at Tuck Johnson.
There is another cut character with a similar name in the game's files, Karen Johnson, presumably his wife. Tuck Johnson and his wife were most likely one of the other "families" living in Andale. This is because it is said that four families survived the great war in Andale but in game there are only two "families."