Old Man Rivers is a grumpy elderly man who lives across the street from Foster's. He is the main antagonist of the episode Neighbor Pains.
Madame Foster and Old Man Rivers have been enemies since he borrowed sugar from her in 1962 and he never returned it. Whenever they see each other they start bickering nonstop until Frankie separates them. He takes a lot of pride in his lawn and especially hates when imaginary friends set foot on it.
In Neighbor Pains, Frankie explains to Bloo that Old Man Rivers hates imaginary friends and especially doesn't like them setting even one foot on his lawn. This is shown when Time Traveling Tina accidentally steps on Old Man Rivers' lawn and Old Man Rivers immediately bursts through his front door shouting. Whenever this happens, Madame Foster begins shouting back and the two argue nonstop until Frankie eventually has to come in and separate them.
Later in the episode, Old Man Rivers' grandson, Young Man Rivers, begins throwing mud at Bloo. In retaliation, Bloo grabs a stack of papers from Wilt and begins throwing paper balls at Young Man Rivers. When Old Man Rivers bursts through his door and proceeds to yell at everyone for throwing paper on his lawn, Madame Foster then joins Bloo and begins throwing paper balls at Old Man Rivers. Frankie steps in yet again to stop the argument, and then Old Man Rivers threatens to tow every car on Wilson Way if any imaginary friends set foot on his lawn two more times. He then gathers up all the trash and goes back inside his house.
Once that was over, Wilt explains to Frankie that the papers Bloo and Madame Foster threw were actually all of the adoption forms, and without them no friends could get adopted. Wilt and Bloo try to get Old Man Rivers' trash back from him under Bloo's alias, Orlando Bloo. Orlando tries to convince Old Man Rivers that he was collecting trash for the needy. Frankie spots Bloo dressed as Orlando, and immediately goes and tries to get him off Old Man Rivers' lawn. She ends up tearing the trenchcoat in the process, revealing Bloo and Wilt underneath. Old Man Rivers warns Madame Foster that that was "strike two," and that if he caught imaginary friends on his property again that he'd tow every car on the street.
When Mac shows up, he comes up with the idea to sneak Bloo into Old Man Rivers' house to retrieve the adoption forms by pretending to go on a playdate with Young Man Rivers. When Mac introduces himself to Young Man Rivers, he begins making faces at Mac and throwing mud at him. When Mac throws mud back, Old Man Rivers catches him and kicks him out, but leaves Mac's backpack inside with Bloo in it.
Bloo retrieves Old Man Rivers' trash and sneaks back outside, but he ends up grabbing the wrong trash. Eduardo then decides to knock on his door asking for the forms back, and that's when Old Man Rivers calls the towing company. The trash Bloo did retrieve, however, ended up being a love letter to Madame Foster that he wrote but never sent. Mac and Bloo used this to blackmail Old Man Rivers into giving the adoption forms back and not towing any cars. Mac then suggests that he talked to Madame Foster and tell her how he felt. Old Man Rivers does this, but then the two proceeded to get into another argument about who's lawn was better, and Frankie had to pull Madame Foster back inside the house.
He is heard speaking offscreen in Bus the Two of Us, telling Bloo to watch where he's going.
In Bad Dare Day, Bloo dares Wilt to roll around on Old Man Rivers' lawn without apologizing. Wilt goes through with the dare but ends up apologizing anyway, declaring Bloo the winner for that round of the Dare Cup.
Old Man Rivers makes his final appearance in Goodbye to Bloo, attending Mac's going away party.
- His name comes from the song, "Ol' Man River."
- Considering his attraction to Madame Foster it is implied he is either widowed or divorce seeing as he has a son and grandson