A native of the Island, Longfellow is old enough to remember previous occasions when the radioactive Fog covered the majority of the island, before its eventual retreat. His indomitable will and physical fitness have served him well into his old age.
Old Longfellow is a seasoned hunter who can recall a fairly large portion of the region's history; from desperate struggle to prosperous hubris. Longfellow is a veritable legend in Far Harbor circles and one of the few guides capable of guiding a person safely through the Fog. His age and experiences made him cynical and he hits the bottle of whiskey a bit too often in recent years.
Longfellow harbors a deep distrust for the Children of Atom. In his youth, he was in a romantic relationship with a girl named Hannah and the two had planned a future together. The cult's followers attacked the pair at their hideaway deep within the Fog and abducted Hannah. Left for dead, Longfellow eventually made it back to civilization. It took him two months to recover from his injuries and by then it was too late for Hannah. The Children's zealots had brainwashed Hannah's mind and converted her to their ways. Hannah was pregnant but suffered a miscarriage due to the radiation she worshipped and was exposed to, claiming it was "Atom's will" for it to have happened. Hannah later fell victim to trappers. Longfellow became an embittered shell of a man, mostly regretting the death of Hannah and his unborn child.
Old Longfellow carries a unique lever-action rifle called Henrietta in Fallout Shelter.
Longfellow is a heavy drinker, often asking if the Sole Survivor can stop for a drink or, when trading, ask if he can be provided with alcohol. He will even openly state that he will celebrate his death with a final toast (if the player character kills him).
Despite the fog driving most people insane (such as the trappers), Longfellow seems to be quite sane and reasonable, though he often claims his limbs are stiff and his bones ache due to the exposure of the Fog.
Longfellow openly dislikes the Children of Atom; disliking if the Sole Survivor joins them and when talking with DiMA when he talks about the possibility of there being peace with them, he openly states he would enjoy fighting them. Interestingly, he disapproves if the Sole Survivor suggests to spare or reason with Sister Gwyneth when talking to Grand Zealot Richter in The Heretic mission.
When Idolized, he will reveal he always wanted a son or daughter to teach what he has learned to them.
He will become hostile if Far Harbor is destroyed.
He will sometimes sing the traditional Irish songs "Wild Rover," "Molly Malone," and "Jug of Punch" when idle.
When picking up junk items, Old Longfellow will actually commend the Sole Survivor for doing so, in direct contrast to several other companions.
While utilizing power armor does not negatively affect Old Longfellow's opinion of the player character as it does for Strong, he will state he is not overly fond of powered armor because "It's too damn loud to hunt in."