Colonel Hogan and his men are far from the only anti-Nazis in the show, and plenty of people they come into contact with have noteworthy achievements and adventures that the five main protagonists only see a little of.
- Olsen, "the outside man," only appears in four episodes of the series, but, according to the pilot, is constantly doing important work for Colonel Hogan and/or living his own life outside of the camp while posing as a German.
- White Russian spy Marya tends to show up at the tail end of some complex plan where she has spent months earning the trust of a German official whose project and/or life she is setting up for a catastrophic end.
- Tiger, the group's main contact with the French Resistance, is viewed as an important fugitive by the Gestapo and saved Hogan's life during an offscreen adventure between episodes.
- Many Allied soldiers whom the Heroes help out escaped from prison camps on their own before reaching Stalag 13. Perhaps most notable is Braden and Mills' group of twenty men from "Reservations are Required." While there were about twenty bigger World War II POW escapes on both sides in real life, less than five of them resulted in more than twenty people making it back to their own lines, unlike Braden, Mills, and their eighteen companions.
- Many one-shot prominent military officers, such as Klink's old friend Major Kronman, General Felix Mercer, Field Marshal Rudolph Richter, and the No Celebrities Were Harmed General Stauffen are plotting to kill Hitler or at least spy on his plans.
- Captain Michaels from "Anchors Aweigh, Men of Stalag 13" arrives in camp after having pulled off a bold solo escape from another camp that involved stealing a truck, a German uniform, and an experimental gun sight that was in the back of the truck.
- In "The Safecracker Suite," Alfie the Artist is a criminal mentor of Newkirk's who has spent decades as a celebrated safecracker but is enough of a patriot to quickly accept a mission to travel behind enemy lines and help Hogan open an important safe.
- "The Assassin" briefly features a Free French soldier who was captured after parachuting behind Allied lines to kill several top Nazis. Hogan liberates the man so he can kill a German atomic scientist. The assassin is wounded and captured while trying to get into the camp, and it turns out the scientist wants to defect anyway.
- The old couple who run a safehouse for the escape network in "The Flame Grows Higher" have fake Gestapo uniforms that they mention have saved their lives many times.
- Klink's fellow kommandants Colonels Bussie and Burmeister from "The Schultz Brigade" seem like ambitious Butt Monkeys who have spent years being subjected to General Burkhalter's Mean Boss tendencies (he tried to make them marry his sister just like he did Klink). They also depart the series preparing to start an Allied military unit of German defectors (albeit more because they're blackmailed into defecting than out of a genuine Heel–Face Turn).
- Wolfgang Brauner, from "Heil Klink" (the brain behind the Nazi financial system), The unseen Baron von Aukburg from "Top Secret Coat" (who is described as a hero to every German boy and a tough fighter), and Colonel Hugo Hauptmann from "Klink for the Defense" (the most decorated pilot in the Luftwaffe) are Anti-Hero examples. All of them are Famed In-Story pillars of German Society who aren't fully committed to the Allied cause (Aukburg is being paid for his spying while the other two want to help the Allies, but only if they can do it without getting killed) but nonetheless choose to sacrifice their comfortable lives to defy Hitler during periods where his defeat is far from certain.
- In "Klink vs. the Gonculator", electronics expert Major Lutz and his contact Lila have an established and familiar relationship and have spent some time smuggling secrets to England during public meetings that they pretend are dates (which implicitly lead to some Becoming the Mask chemistry).
- In "The Most Escape-Proof Camp I've Ever Escaped From", Malcolm Flood is introduced as a Prison Escape Artist who has been giving the Nazis a headache with constant larger-than-life escape attempts.
- Dr. Suzanne Lechay from "Hogan and the Lady Doctor" was previously held prisoner by the Nazis and forced to aid their energy program, escaped, and spent a year in hiding before being sent to help Hogan infiltrate and sabotage another Nazi energy project.
- In "How To Escape from Prison Camp Without Really Trying", an undercover Hogan spends a dinner date pumping a German woman for information, only for her to end the date by revealing that she is an undercover British agent named Audrey St. Laurence who knew what he was doing the whole time.
- In "D-Day at Stalag 13", Lili von Scheider married a German general to spy on him and has spent years struggling with her feelings for him while being left unsure about what to do after her paranoid handlers cut ties with her.
- In "Casanova Klink", a group of underground agents are planning a big raid on a Nazi installation when Hogan stops them from heading into a trap and gives them an alternate target.
- Colonel Crittendon, an unseen character from "The Crittendon Plan" whom the incompetent recurring Colonel Rodney Crittendon is mistaken for, is an expert theorist in allying with local partisans for commando raids, and London officials urge the heroes to break him out of a prison camp to help with an important operation (although they end up breaking out the wrong Crittendon).
- Leni Richter from "Carter Turns Traitor" is a chemical warfare expert who has been sabotaging her program in order to rob the Nazis of a weapon and tries to kill Carter for that same reason before learning he is a Fake Defector.
- Robert Morrison/Hans Teppel from "Bad Day in Berlin" is a German-American Allied spy who gave up his American citizenship to go undercover with the Nazis. He is an accomplished agent with his own network of allies who develops a quick rapport with Hogan while they are working to capture a Nazi agent. He also arranges for a Resistance Cold Sniper to be waiting to shoot the target in case he and Hogan fail to capture the man.
- "The Missing Klink" has two unseen examples.
- Hans Wagner is described as a brilliant and charismatic leader who warrants having a huge military presence guard the holding area where he is being kept before his scheduled execution. Wagner's fiercely loyal younger brother and Hogan are out to free Hans at all costs.
- Agent Nimrod once infiltrated the German high command, is even more hated by the Nazis than Wagner is, and somehow gets wind of the heroes’ operation to rescue Wagner, sneaks into the prison camp, and leaves a set of weapon plans for them to smuggle out of the country. note
- Dr. Zagoskin from The Witness is a Russian rocket scientist who fell out of favor with the Soviets and ended up working for the Germans but has secretly been planning to sabotage his rocket so that, once he knows his theory will work, it will blow up himself and a bunch of German officers and scientists instead of an Allied target.
- Major Blair from "The Empty Parachute" plays a pre-internet Voice with an Internet Connection role in helping the heroes disable a Nazi bomb and references how such bombs have been keeping him and his unit busy, sometimes with fatal results.
- The eponymous Lady Chitterly from the "Lady Chitterly's Lover" two-parter journeys from England to Germany at the behest of her British Nazi husband, is horrified by what she sees of the Nazis' governing methods, and has been plotting to undermine her husband's plots and kill him when Hogan encounters her and gives her another outlet for her anger and renewed loyalty to England.
- Captain Steiner from "The Dropouts" is an S.S. officer who (despite that branch's general loyalty to Hitler) ends up trying to desert to Switzerland along with a pair of atomic scientists out to keep their work away from Hitler. His background and motives for helping the two men (to whom he seems highly loyal and protective) are only subtly hinted at, but feel like they could have made the basis of a whole episode on their own.
- Hans Strausser/Major Martin from "The Meister Spy" is a loyal German spy, but he sounds like a Villain Protagonist of another story that the heroes only see the end of (spying on the Allied generals' staff, having a career that other German spies follow with awe, having a relationship with a female spy who helped him on some of his jobs and infiltrating a bomber crew before tricking them into landing in German territory). After getting a good idea of Strasser's accomplishments, Hogan notes, "He's a hero all right, but for the wrong team."
- In "That's No Lady, That's My Spy", Master of Disguise Oskar Danzig has spent a long time staying ahead of the Gestapo and saving his life after he is wounded is seen as a vital mission.
- In "Hogan's Double Life", the leaders of two separate underground cells associated with Hogan's Heroes have clearly had a lot of past adventures together, as each knows that the other is a Resistance member when they meet on the same job by chance, and they ask about each other’s families.
