Season 16 of Survivor had a particularly stunning example of this. Near the endgame, there were five contestants left - 1 male and 4 females. Erik won the Immunity Challenge, so the four women plotted to get him to willingly surrender his immunity. They sent one of their group to convince him that he needed to give it up to "redeem" himself. Natalie herself lampshades the absurdity of the scheme possibly succeeding, stating "who would fall for that?" You'd expect: Erik to tell Natalie exactly where to stick her request, knowing that this game is based upon the concept of "Looking out for #1." Instead: He gives her the immunity necklace just before the elimination vote. No points if you guess what happened next.
His move was so epically stupid that James, the guy known for getting eliminated while sitting on two hidden immunity idols, stated that Erik had beaten him for the title of "dumbest Survivor ever."
Earlier in the same season, after finding the Hidden Immunity Idol, Ozzy created a fake one and put it where he found the real deal, hoping to trip up whoever found it. He's not really an expert craftsman, though, and the best he can make is a poorly carved stick with a misshapen smiley face on it. A couple episodes later, Jason finds said fake idol. You'd Expect: That Jason would be suspicious of how it looks cheaply-made, and subsequently realize it's a blatant fake and someone else got the real one. Instead: He buys it, hook line, and sinker. So much so that when his ally Eliza comes under fire, he plays the "idol" to protect her, and is genuinely shocked when Jeff announces it's not the real thing.
Marcus in Gabon had one of the swiftest and dumbest downfalls ever. A tribal swap at the Final 10 happens, giving his tribe, the Kotas, a 3-2 advantage on both tribes. All he has to do is secure Susie after she got 3 votes last Tribal Council and take out the Final 2 Fang alliance of Crystal and Ken. You'd expect: When Susie asks Marcus if he can be trusted, he says "yes, you can, Susie. Which of the two do you want to go home?" Instead: He either ignores or doesn't answer her or give her any trust, and instead goes to Crystal based solely over the fact that he was best friends with her cousin. He makes her an offer to replace Susie in her alliance as #6 if she votes off her closest ally, Ken. Not being a complete idiot, she rats him out to Susie and they handily vote Marcus out 3-2.
Africa: Lex, who has just received an unknown vote during what he believed what was going to be a unanimous vote-off against Clarence at the merge, is hell-bent on finding out who made that throwaway vote against him. He eventually comes to the decision that his former tribemate Kelly that cast the vote, when in fact it was Teresa (who was a former member of the opposite tribe). You'd Expect: In an era of Survivor where voting along tribal lines was the norm - even with the low justification that it was Kelly that cast the vote - that Lex would at least wait until he had significantly Pagonged the former Samburus to get rid of Kelly. Instead: He press-gangs his allies into voting for Kelly based on his "gut decision." Kelly, obviously pissed for being on the wrong end of a Witch Hunt, flips to the Samburus to get rid of Lex, and would have succeeded in doing so had Brandon not held an even bigger Idiot Ball than Lex's.
All-Stars: Lex pulls a boneheaded move just before the tribal merge. At the tribe change-up, Amber ends up separated from her Chapera tribemates, and is put with the Mogo Mogo tribe (who are now in the Chapera camp). Lex (and the rest of his tribe members) have seen that Rob is highly protective of Amber, and has already proven himself to be a superior force in challenges. At the immunity challenge, Rob goes to Lex immediately after and tells him he will be protected, provided that Lex protects Amber in turn. You'd Expect: That after already eliminating two good competitors (Richard and Ethan) with backroom deals, he would look out for himself and eliminate Amber at the next Tribal Council, which would (a) put his tribe ahead of Rob's team, (b) demoralize Rob and (c) give Lex an opportunity to eliminate an opposing force before he makes any more moves. After all, Lex has already seen Rob carry most of his original team through half the game. Instead: Lex takes Rob at his word, and spares Amber by voting out another loyal team member (Jerri). In the following episode (where the teams merge as Chaboga Mogo), Rob tells him point-blank that he's not going to help him, and Lex is swiftly eliminated that night at Council. Following this, Mogo Mogo gets Pagonged by the tight-knit Chapera. For his part, Lex does admit he seriously screwed up when he did what Rob asked. Later On: When they're down to five people, Chaboga Mogo heads into Tribal Council with Rob wearing the Immunity necklace. At this point, Rob has planted a lot of discord between Tom, Rupert and Jenna (with the latter two realizing that Rob is playing them). You'd Expect: The three players, who all know that Rob has been tight with Amber since the beginning of the game (an alliance which he has told them multiple times he wouldn't break), would eliminate Amber immediately and take out Rob at the next Council, leaving the three of them left. Instead: Rob convinces Rupert (who knows Rob was tricking him into fighting with Tom) and Jenna (who knows she's a liability) to vote out Tom, which allows Rob and Amber to coast through unchallenged to the final Tribal Council.
Heroes Vs. Villains: Late in the season, the Villains outnumber the Heroes. Sandra (a Villain) goes to Colby and Rupert (the two Heroes left) and tells them that Russell can't be trusted. She explains that he played the Heroes team for fools when they gave him their hidden immunity idol, and that he's the one who's been leading the rest of the female Villains (as well as being the one that destroyed Sandra's alliance with Courtney). She tells them this no less than three times in the span of two episodes. You'd Expect: That, given how Russell already played an immunity idol post-merge and knocked out J.T. (after telling the Heroes that he had previously played it to save himself, something that never happened), and already showed that he broke his word multiple times, they would at least try Sandra's advice and knock out Russell before he becomes a bigger threat. Instead: They don't, proceed to try and vote her out instead, and both get systematically eliminated by Russell's alliance, leaving only the Villains left in the final three. Sandra proceeds to call Colby and Rupert out on this during the final Tribal Council meeting.
Meanwhile, Russell goes through this hard at the Heroes vs. Villains final seven: at the time, the only contestants left are his alliance with Parvati, Danielle, and Jerri, Sandra, who's aligned with nobody, and Rupert and Colby on the outs. But Russell is beginning to become suspicious of Parvati and Danielle, on account of the two of them keeping a HiddenImmunity Idol secret from him (which wasn't all that wise, either). You'd Expect: That Russell would keep his core alliance with Parvati and Danielle strong, given that they've been working together from the get-go (not to mention that the two are at this point the only ones left that will talk to him), just to be sure that the three of them will go to the end. Instead: He decides to pit the two of them against one another in hopes of separating them. When Danielle calls him out on it at Tribal Council, he proceeds to talk to Danielle like she's crap in front of the entire jury, which - if Courtney's reaction◊ is any indication - destroyed whatever slim chance was left of him winning. Or, for that matter, avoiding a Humiliation Conga.
Russell's entire strategy: convinced that he is the best player ever, he proceeds to lie, backstab and generally screw around with just about everybody. By the time that the show is down to the final three, Russell has blindsided and backstabbed his alliance, people he made temporary alliances with and just about everyone else on the jury. The other two members of the final three are Parvati, his former ally who is regarded as a skilled and dangerous player, and Sandra, who basically hates his guts, spent most of the season trying to get him voted off and who may not be a strong player, but has the advantage of not being Russell. You'd Expect: At some point during the season, Russell realises that pissing off the jury isn't going to end well. You'd really expect that by the time of the Final Tribal Council, he might be just a little bit worried that he's up against his much more likeable former ally and his extremely entertaining enemy, and the jury has no reason to like him whatsoever. Instead: He remains convinced of his own superiority, and naturally loses in a landslide: Sandra gets six votes, Parvati gets three votes, and Russell gets no votes. Even better, at the reunion, Jeff tries to explain that backstabbing the jury will make them dislike you. Russell refuses to acknowledge that.
Nicaragua: It's the final six, Jane feels a bit on the outs in her four-person alliance with Chase, Sash, and Holly. The alliance's immediate target Fabio wins Immunity, and he tries to protect his ally Dan by convincing Chase that Jane's the bigger threat. Chase immediately takes the idea to Sash and Holly, and the three soon resolve to vote Jane off (forgetting, incidentally, that Fabio made the suggestion in the first place). You'd Expect: That they would blindside Jane. Dan and Fabio want her gone, and Chase and Sash are the ones with hidden Immunity Idols, so there wouldn't be any real way that she could protect herself if votes were cast her way. Instead: The tell Jane to her face that she's the next to go. Not only does Jane reveal the alliance at Tribal that night, but now Chase and Sash have to take Holly with them to the Final Three, lest they have a vicious attempt on Jane's part to turn the jury towards Dan or Fabio (the latter of whom ruined that plan with an immunity win).
Redemption Island sees Russell, and by extension all of the Zapatera, getting hit hard with this trope. To elaborate, this is the first season that he's playing alongside people that had the chance to see him in action; they know exactly what he's all about. One of the first things he does is promise his tribe that he'll be playing a different game this time. You'd Expect: That Russell actually would play a different game this time, or at least pretend to do so until the merge, when he would likely have the better numbers. In the very least, they wouldn't have been so likely to have their own What an Idiot entries. Instead: He runs the exact same play in the exact same way, from swiping clues to the Hidden Immunity Idol to forming his usual harem (while dismissing anyone who isn't built like a Laker Girl), to pigging out on the tribe's provisions while they fish. Not surprisingly, he's marked as a threat, his tribe throws a challenge to off him, and the vote is split three ways on the off-chance he did find the idol. (Oh, forgot: he didn't even bother making sure no one was watching.) On the re-vote, they have five available votes and two options while Russell's side has only one available vote and one option. (Stephanie doesn't exactly help their cause with her irritation at David's spiel or her scorching tirade at Tribal Council, which loses them a potential swing vote.) One guess as to who goes.
Extra points however also go to his Zapatera tribe who wanted him gone, FAST. You'd Expect: The group just wait until a normal immunity challenge loss to vote him out (Or just vote off his allies, so Russell will be forced to work for them). They know Russell's game and know he's not to be trusted and the same would likely (or should have been) with the other tribe should a tribal mix occur and, while as sneaky as Russell can be, he's pretty decent in challenges, something which could help them avoid tribal councils to come and then come out on top at the merge. Plus, they saw Rob already survived 2 tribal councils in a row. Instead: They throw the THIRD immunity challenge to boot him out, which managed to snowball their tribe into repeated losses, having their tribe decimated before the merge and then mostly kicked out one by one after the merge leaving an all Ometepe final six.
Next episode, with their sugar daddy gone, Russell's concubines are alone against the Zapatera Six. You'd expect: Knowing they're basically begging for their game lives, Stephanie and Krista would try to make a little peace with the enraged Zapatera. They might even be able to replace the fifth or sixth wheel and have a legitimate crack at overtaking the Ometepe (who already dropped one fringe player through the trapdoor). Or, if they can last until the merge, swing over to the Ometepe, and use them to get back at their former tribe and go deep into the game. Any way you slice it, a powerful bloc whose votes decide the power center for the rest of the season. Instead: Krista confronts the Zapatera Six about the folly of their decision, albeit in a manner far from Up to Eleven. Stephanie, of course, does Stephanie things. Two up, two down, game, set, match. (The only thing that saved them earlier was their challenge win, which the Ometepe used to sink another player on the periphery.)
And speaking of the Ometepe tribe, they managed to pull this and held an Idiot Ball for the entire season, . One tribe gets Russell, and they get Boston Rob. Now they've all seen Russell play, and they have also seen Rob play and even knew who he was. You'd Expect: That they'd realize that he is Dangerously Genre Savvy and should get him out ASAP because he's got a huge target on his back, has more experience, has the producers on his side, there is nothing saying you can't immediately vote him out (as Russell found out pretty fast). Instead: Only Kristina realizes this while everyone else except Francesca seems to be staring at Rob like he's a savior and then looking at Phillip asking, "Is this guy serious?". Kristina then goes on to find the hidden immunity idol within the first three days and immediately intends to use it to get Rob out of the game (which failed). They then vote out Kristina and Francesca and let Rob do all the work for him, letting it progress into the solo game when the producers throw one puzzle after another at Rob (the only challenges he gets to compete in, mind you) and are then surprised that Rob seems to be taking someone hated by everyone else (Phillip and Natalie) over them, and Ron won unsurprisingly.
Episode 7-8 of South Pacific earns Ozzy a place here due to his choices regarding Redemption Island. At the final twelve, with one person on Redemption Island, Savaii go to Tribal Council and are expected to vote someone out to join Christine on RI. Ozzy confides in the tribe that he had a dream that he would get voted out, go to Redemption Island, battle and defeat Christine, and rejoin their tribe making sure that they go into the supposed merge 6-6. This plan is insanely risky in that the merge is merely assumed to be coming up, and Christine is still there, with no telling if the challenge will be one Ozzy will excel at (given how she's even beaten Mikayla, a highly physical player). Furthermore, Christine has been seen giving the finger to her old tribe and leaves no doubt she'd jump to Savaii in a heartbeat if she ever came back. Of important note is that this plan also involves putting trust in and keeping Cochran, whom most of the tribe has been treating as a Butt Monkey/verbal punching bag for the last 21 days. You'd expect: The rest of the tribe to ignore Ozzy's insane plan and instead vote out Cochran, not taking the risk that he'd swap to Upolu after 21 days of verbal jibing. Then they could swing Christine to their side and use her challenge prowess displayed on Redemption Island to their advantage for the upcoming 6-6 voting tie the entire tribe was anticipating. Instead: They go through with it, keep Cochran, vote out Ozzy, Ozzy beats Christine in the duel and gets rid of her. After a tie at the Tribal Council vote, Cochran flips on his high-school-esque tribe and votes out one of their members with Upolu, who have been treating him well since the tribes have been merged (exactly how Christine indicated she would have aided the Savaii). And while he's with his new peeps, the other Savaii are left fighting for their game lives. Same season: Brandon Hantz (nephew of Russell Hantz, also on this list) wins immunity right before the final Redemption duel. He then gives it to an ally and is immediately voted off, similar to Erik's entry earlier on this list (though no one appeared to have planted any seeds in Brandon's head as the Brigade did Erik's).
Episode 1 of Philippines sees Zane Knight making an alliance with both the women and the men secretly. He intends to vote out Russell due to him being a threat to his power. The rest of the tribe agrees and prepares to vote out Russell. You'd expect: Zane to not reveal to Malcolm and Russell that he already forged an alliance with the women, and to accept the offer to vote out the latter with the rest of his tribe. Instead: He reveals to Malcolm and Russell that he already formed an alliance with the women, and asks his tribe to vote him out, stating it's part of a strategy. He gets voted out unanimously for his untrustworthiness.
Later in that season, Jeff Kent tells Carter that they are voting out returning member Johnathan Penner. You'd expect: Carter wouldn't accidentally tell Penner they are voting him out. Instead: Carter accidentally tells Penner they are voting him out.
Borneo: Sean has decided that he wants no part of the lying, scheming and backstabbing. Instead, he has come across a new strategy: he will cast his vote in alphabetical order, and make it clear to everyone that this is all he will do, so everyone knows that if he votes for them, it's nothing personal. You'd Expect that at some point he realises what a moronic idea this is. Instead the other Tagis realise what a stroke of luck this is and all cast their votes alphabetically: because the Pagongs have names in the first half of the alphabet, they get taken out one by one and Sean takes forever to realise that all he's done is give everyone else a free vote to take out their opponents.
Cagayan: In the first half of Episode 1, David manages to redefine this trope, with his "play the individual half of the game during the tribal half" strategy. Let's start from the top: The tribe elected him as leader, then Jeff tells him to select whom he thinks is the weakest link on the tribe by first impressions alone. You'd Expect: He'd pick someone like Spencer or J'Tia, who by looks alone aren't heavy hitters. Instead: He chooses Garrett, the only one on the tribe who could take any of the Brawns tribe, which pisses him off, vowing revenge. The Result: When the Brains lose the challenge, Garrett seizes the chance to get David eliminated, and succeeds. David is the first person voted out, 4-2.
Then, Garrett himself gets struck with this. The tribe loses the next challenge, and have to vote again, and since J'Tia lost it for them, it's obvious whose currently in his sights. But Tasha and Kass are hesitant to do so, since they want to use her for a goat. You'd Expect: That Garrett just lets things run their course and makes the argument at Tribal Council to boot her. Instead: He hosts an impromptu tribe discussion where he blatantly says J'Tia is the one to go and bans strategy talk for the remainder of the afternoon. The Result: This only cements Tasha and Kass's concerns, and they blindside him, 3-2, leaving his ally Spencer on the outs.
Episode 6 (the merge episode) gets two grand ones for Sarah and Kass respectfully. 1) Sarah sees that she's the swing vote between the two alliances, and is torn between them. You'd Expect: She'd think long and hard about her decision. Instead: She pretty much flaunts this status, and causes Tony's alliance to turn on her. 2) Adding on to this, Kass becomes concerned with how much power Sarah has and is annoyed by her indecision. (She off-screen sticks with the Appari gang.) You'd Expect: She calms down, and talks to someone about this. (She does so, but thinks that everyone is just trying to butter up to Sarah.) Instead: When Trish (who's in the rival alliance) comes up to get her to vote out Sarah, she jumps at the opportunity. The Result: Sarah is blindsided, 6-5, and Kass has destroyed any chance of winning the game.
But wait, there's more! (Tell me why the Redemption Island is considered the dumbest cast again) It's Episode 8, and Tony and the Solana alliance are up 6-3. Tony sees that L.J. (who is in his alliance) is a major threat, and is entertaining the thought of backstabbing. You'd Expect: To NOT do this. Instead: Well, here we are.
Woo has won the immunity and got to vote out the last castaway between Tony and Kass and he promised Kass he'll vote out Tony. You'd Expect: Woo would keep his promise and vote out Tony not only taking out the biggest threat left but also bringing himself to the final 2 with someone who has enemies with pretty much everyone. Instead: Woo decides to stay loyal to Tony, his ally from the beginning, and votes out Kass, guess who wins.