Bob is a species of tree that is a result of mutation, progressively growing from within Harold.
Bob sprouted from Harold's head sometime between 2162 and 2208, after Harold was exposed to the Forced Evolutionary Virus at the Mariposa Military Base. In the beginning, Bob was a small sprig but its growth accelerated, turning into a full-sized tree, overtaking Harold, and rooting itself to the ground in the Capital Wasteland region. As of 2277, the two have been rooted to the location for over two decades.
Bob and Harold were later discovered by several people who began to worship the discovery, founding a group known as the Treeminders. They started worshipping the mutant tree collectively as a deity, of which Harold reports Bob's disdain for. Bob does not dislike all the Treeminders, as Harold points out he and Bob's adoration for Yew, the child of the group.
Harold considers Bob his friend and speaks to him as if he was thinking aloud. Harold will sometimes jokingly refer to Bob as Herbert, which he says drives Bob crazy. Harold will share some of the mischief he and Bob have caused over the years, such as Bob telling him to make the Treeminder Maple stand on his head for an entire day.
Harold details his past with Bob, explaining how after the two of them were rooted in place, Bob subsequently began to blossom, extending its reach outward, resulting in a lush green habitat named Oasis. Seeds that have taken root in the region are a result of seed pods carried by the wind, affectionately called "Herbert's seeds" by Harold.
When the Lone Wanderer approaches Bob and Harold for the first time, Harold will share that he was able to see their approach through the leaves of other trees, and although impressive, it makes Bob jealous. Harold will share his sadness at he and Bob's current state, confiding that living the way they are is miserable to him, to be trapped in one place for an eternity, and asks the Lone Wanderer to kill he and Bob. The player character can speak with Harold and Bob about the request and they will be steadfast in the request, not wishing to remain there for hundreds of years, explaining that they can't kill themself and they wish to be at peace, resolute in the decision to be "just me and Bob until the end."
- Oasis: Harold asks the Lone Wanderer to kill he and Bob so that they can finally be at peace. The Treeminders that worship the tree ask for one to consider alternatives.
- Lone Wanderer: "What's with all the names? Bob, Herbert and Harold? I don't get it."
Harold: "I was once a man a long time ago named Harold. Something in me changed and a weird little tree started growing right out of my head. It kept getting bigger until I ended up stuck inside. When people would ask about it, I decided to name it Bob. You know, like a friend or something. Sometimes I call him Herbert instead of Bob, because I get bored and I think it's funny. So long story short, call me Harold!"
- Lone Wanderer: "You want me to murder you?"
Harold: "Oh no, no, no. It wouldn't be murder. You'd be doing me a favor. You see, I've been stuck here for over two decades now... rooted right into the ground. The only friends I've got are Bob and those weirdos out there who think I'm a god."
- Lone Wanderer: "About those Treeminders..."
Harold: "Oh, don't get me started on them. I'm liable to talk about them all day! It even drives poor old Bob crazy."
- Lone Wanderer: "Which Treeminder do you get along with the best?"
Harold: "Actually, the kid is the nicest one of all. Yew's her name. She sneaks in here sometimes and just lets me talk about stuff I wanna talk about. Bob really likes her too, cause she makes me happy."
- Lone Wanderer: "Um... I must be dreaming."
Harold: "Sigh. I wish I was too. Then me and Herbert could be the best of friends and live side by side. He's the tree, you see. We're old pals... the best of buddies and we know each other inside and out; literally. Well, his name's really Bob. I think it's funny to call him Herbert. But I don't think he thinks it's that funny."
- Lone Wanderer: "If people thought I was a god, I'd exploit it for all it's worth!"
Harold: "Hey, I thought that too... at first. I had them sing me songs, I made them do stupid dances and things like that. Bob even told me to make Maple stand on his head for a whole day! After a while though, it just gets boring. Then it becomes a nuisance and now it's completely driving me nuts!"
- Lone Wanderer: "How is it you're causing all of these things to grow around you?"
Harold: "It's kind of embarrassing really. Once a year, Bob decides he's going to go ahead and start growing these weird pods filled with tiny seeds. Well, all it takes is a good wind and the seeds just fly everywhere. I call them Herbert's Seeds. He hates that!"
- Lone Wanderer: "Seeing me approach Oasis is quite a feat for a living tree."
Harold: "Maybe I'm just losing my mind from all this boredom. I swear if I try real hard, I can see all around me like my eyes are in every leaf on every tree. I think it's making Bob kind of jealous, cause he was the first tree in my life and all that."
- Lone Wanderer: "Well, hopefully your troubles will be over. I'm here to help."
Harold: "You have no idea how glad I am to hear that. Or, we're glad to hear that... me and Bob. I had you brought in here to ask a very simple favor. Would you please kill me? "
Lone Wanderer: "Kill you? You can't be serious!"
Harold: "Completely serious. You'd be doing me a favor. You see, I've been stuck here for over two decades now... rooted right into the ground. The only friends I've got are Bob and those weirdos out there who think I'm a god."
Lone Wanderer: "Look, I really don't want to kill you..."
Harold: "Of all the Wastelanders I had to bump into it has to be one with a conscience. Let's keep it an open invitation then. I don't want to wait until the next person visits, it could be years."
Lone Wanderer: "Can I have some time to think about it?"
Harold: "Of course. I know this is an unusual request, but hey, I'm an unusual tree. Well, Bob is anyway... We'll just keep it an open invitation then. I don't want to wait until the next person visits, it could be years... you're all I've got."
- Lone Wanderer: "Hey, life is a gift. Even if it lasts a long time, be glad you have it!"
Harold: "I've tried to stay happy, really I have. Bloomseer Poplar thinks I'll live for hundreds of years... maybe even more! Can you imagine THAT? Stuck here for centuries? I can't do it, I just want to be alone. Just me and Bob until the end."
- Lone Wanderer: "Ok, I'll do it."
Harold: "You will? Oh! You've made us so happy! Isn't that right Bob? Just give me a little time to say goodbye to good old Bob and then I'll be ready."