Nice Job Breaking It Hero / My Little Pony: Friendship Is Magic

• In "Dragonshy", Rarity could have easily lured the dragon out of the cave had she not told him she would guard his treasure hoard. After the dragon kicks her out, Twilight Sparkle calls her out on it.
• In the episode "Swarm of the Century", Twilight Sparkle uses her magic powers to stop a swarm of locust-like Parasprites from eating all the food in town. It works; the Parasprites stop eating food and go after everything else.
• In "Sonic Rainboom" Rarity's mission to provide moral support for Rainbow Dash suddenly turns into Rarity's runaway ego trip that only hastens Dash's collapse into a quivering nervous wreck.
• In "Over a Barrel", Pinkie Pie tries to settle a territorial dispute between settlers and the native buffalo herd by singing about sharing. The sheriff and the buffalo chief finally come to an agreement...that it was the worst performance they'd ever seen. When the buffalo are on the verge of backing down from their threat of a stampede, Pinkie Pie's ill-timed reprisal of the song triggers the chief's Berserk Button.
• Rainbow Dash's advice to Apple Bloom to try as many different things as rapidly as possible in order to find her Cutie Mark got carried over to the Cutie Mark Crusaders. Perhaps if they weren't constantly changing plans they might succeed.
• The mane ponies' efforts to have the reality of the Gala meet their expectations in "The Best Night Ever" end up wreaking havoc at the Gala itself. It turns out Princess Celestia had hoped this would happen in order to bring some life to the event.
• In "The Return of Harmony, Part 1" the fight between the Cutie Mark Crusaders pretty much caused Discord to wake and escape from his weakened prison.
  • In the second part of the two-parter episode, Twilight's guess Discord's riddle meant the Elements Of Harmony were in the maze was wrong and because of her not thinking the riddle out more carefully, her friends were broken and Mind Raped by Discord for nothing. What's worse, Discord takes great pleasure in rubbing it in her face.
• Pinkie Pie messes up things again in "Luna Eclipsed", when she keeps freaking out over Luna doing something and taking it as Nightmare Moon doing something. This wouldn't be a bad thing, but Luna's just come back from 1000 years stuck on the moon and has no idea how anything runs. The third time Pinkie Pie does this, Luna initiates a Rage Quit and declares Nightmare Night cancelled.
• Twilight breaks herself in "It's About Time". A battered and broken Twilight from the future appears briefly in the library and tries (unsuccessfully) to warn her past self about some oncoming disaster to take place between now and next Tuesday morning. Present Twilight misses the important part of the message and immediately freaks out, spending all of her time trying to deduce what's about to happen and, if at all possible, prevent it... but nothing really bad actually happens. Twilight finds a spell to go back in time, and tries to warn her past self not to panic — but in failing to deliver the message, CAUSES her past self to panic.
• This happens again in the season two finale "A Canterlot Wedding". Seeing the very questionable actions of Princess Cadance leads Twilight to believe that she has somehow become evil and tries to warn everypony about what she's learned. This makes her come off as rather crazy and her friends end up shunning her, including Celestia. Surprise! Cadance really isn't evil, but the Cadance that was acting like a total Bridezilla is actually an EVIL IMPOSTER... Specifically a new foe, the Changeling Queen Chrysalis, impersonating Cadance and using her love for Twilight's brother, Shining Armor, to fuel her power. By the time Twilight and the real Princess Cadance arrive to stop her, the Queen already became too strong for even Celestia to handle. She even points out that they could have stopped her sooner if they all had listened to Twilight in the first place, although as Twilight herself points out a moment later, her disguise would have fooled everypony anyway. It was only because the real Cadance was Twilight's fillyhood friend that she grew suspicious of Chrysalis!Cadance to begin with, and even then she only realized the real truth after finding the real Cadance in the Canterlot caves who informed her of the imposter plotting to take over Equestria.
  Applejack: Sorry, Twi... We should have listened to you.
  Twilight Sparkle: It's not your fault - she fooled everypony!
• Twilight Sparkle pulls practically the exact same blunder she did with the Parasprites again in "Bats!" She tries a spell that will change the vampire fruit bat's tastes so they don't like apples and it works... with the side-effect of transforming Fluttershy into a vampire fruit pony with an even bigger appetite than all the bats combined.
• In "Somepony to Watch Over Me", Apple Bloom secretly runs away from home while Scootaloo and Sweetie Belle take turns posing as her in bed. While Sweetie Belle is in bed, Scootaloo hides in the closet. Applejack then says she doesn't have to look after Sweetie Belle anymore, and Scootaloo shouts out loud, "Wow! Wait until Apple Bloom hears about this!" Then the jig was up!
• In "Equestria Games" the Power Nullifier to prevent cheating from the unicorns prevents them from doing anything to stop the giant ice cloud as it plummets toward the stadium.
• In "Twilight's Kingdom Part 2":
  • Celestia's tradition of showing off the heroes of Equestria (notably, Princess Twilight's ascension) in the stained glass windows of the royal halls comes back to ruin her plan to keep knowledge of Twilight secret from Tirek. He probably would have found out anyway, but still...
  • Discord puts his own spin on most of the windows in the palace, but forgets to do that specific one, or at least hadn't gotten to it by the time Tirek noticed.
• In "Amending Fences", we find out that Twilight's Establishing Character Moment from the very first episode broke another pony altogether: Moondancer was a very shy pony who was starting to come out of her shell as she considered Twilight the closest thing to a friend. When Twilight snubbed the party invite due to her studies and was ordered to go to Ponyville by Celestia, ignoring the party and not even telling her friends goodbye, this turned Moondancer into a reclusive shut-in, focusing only on studying. It takes Twilight five years (in Real Life terms) to realize she made a big boo-boo.
• And Pinkie Pie gets a hat trick. In "Rock Solid Friendship", Maud Pie and Starlight Glimmer are bonding and becoming friends, but not at Pinkie Pie's pace. Her constant pushing ends up driving Maud Pie out of Ponyville and into the Ghastly Gorge, nearly to be Eaten Alive. As well, we find out that Maud had unwittingly revealed a special type of stone to Starlight that would suppress the magic of a Cutie Mark back when she was starting up "Our Town".
• In "Shadow Play", Twilight discovers that Star Swirl the Bearded and his allies, the Pillars of Equestria, had sealed themselves in limbo for over a millennium in order to contain the villainous Pony of Shadows. Eager to meet her idol, she works to find a way to rescue the legendary ponies from their fate. She ends up succeeding in this regard after her friends gather items belonging to the Pillars. Unfortunately, the Pony of Shadows is brought back right along with them.