Professional wrestling in general is full of these kind of moments due to its on-the-fly writing style and the relative secrecy most wrestling companies work under to avoid spoilers. Frequently story lines are started and then squashed due to one or more of the performers dying, quitting, being fired, or being injured. Angles can also suffer heavily from attacks by Moral Guardians and by Executive Meddling. It's worth noting that since Professional Wrestling is an ongoing medium, users should wait before posting recent examples until the actual storyline plays out.
In 1990, the WWF was hyping a giant egg, whose contents would be revealed at the Survivor Series. The egg's hatching turned out to be a rotten moment, as what emerged was a huge chicken-like thing called The Gobbledy Gooker (played by Eddie Guerrero's older brother Hector in a hideous suit). WrestleCraphas more. Also, they name their yearly people's choice award for wrestling's worst thing, The Gooker.
The Gooker has been referenced since then, but it's usually been to reference just how horrible the idea was.
And it wasn't a chicken, but a turkey - which makes perfect sense when you recall that Survivor Series used to be held on Thanksgiving Day. The most hilarious aspect of this episode was that for weeks, both wrestling commentators and fans were wildly speculating on what could possibly be inside the egg. Some even wondered if a new wrestler was about to make his debut. I mean....IT'S AN EGG! Did they actually think that anything other than a giant bird (or maybe a dinosaur) was going to emerge from it?
It was allegedly going to be gimmick used for the debut of Mark Callaway. They then decided against it, and his gimmick led to his debut as the The Undertaker.
A Halloween episode of WWE SmackDown! has Smackdown General Manager Stephanie McMahon encounter Raw GM Wrestling/Eric Bischoff wearing a Vince McMahon mask in her office. After doing a bad impression of Vince, he rips off the mask and gives her a long, passionate kiss, which she resists at first, but slowly begins to enjoy. Aside from a very small inside joke during Eric Bischoff's trial on the December 5, 2005 episode of RAW, it is never referenced again.
WCW's entire "Blood Runs Cold" angle was rather infamous for being a BLAM that was several months long, and ate up time on several of their shows. At a time when the entire WCW is gearing up for war with the nWo, and every storyline seemed to gradually weave its way into that, there was always one segment each night that involved a bunch of Mortal Kombat knock-offs fighting over a helmet for some reason. Once the whole thing was over, Glacier and Wrath disappeared for months, Ernest Miller was demoted to a jobber, and Mortis got mocked by Raven, eventually lost his mask, and became Kanyon. Glad to find out that this storyline, which was hyped for months and played out (badly) over several more months, was so damn important, guys.
WCW was prone to creating unintentional BLAMs. They did not allow their commentators to view the backstage segments so that the commentary would be more spontaneous... unfortunately they just looked clueless more often. One notorious example was a segment where the nWo beat Ric Flair up in some random farm field. Flair later hitchhiked to the arena in a truck filled with turnips. When he finally made it to the arena, dirty and stumbling around dazed holding an axehandle, the commentators - who didn't see the beating or hitchhiking scenes - wondered if he was drunk, rendering the whole thing a BLAM.
Not to mention, Dustin Rhodes is Seven... well, for a few vignettes anyway. The Standards and Practices department at Turner hated the character and wanted him gone, mostly because WCW made Seven look like a child abductor/molester. Just before Rhodes made his debut as Seven, Vince Russo was hired to be the head writer of WCW, and he debuted the character with a spooky Undertaker-like entrance - then had Rhodes rail against that gimmickand his Goldust gimmick in one of Russo's many Worked Shoot promos to bury the gimmick once and for all.note The character's appearance was based on the title character from the 1995 movie Powder.
On a 2003 episode of Raw, there was a note found backstage saying "I Still Remember" left for Booker T. Booker T was alarmed by this and seemed to be frightened by what it meant. It was never mentioned again, although it was speculated to be a sign of Goldust's return which didn't happen until quite some time later. (They could have at least hung a lampshade on Booker's earlier discovery of that note.)
During WCW's Capital Combat in 1990, Sting was trapped in a cage with metal bars at ringside by the Four Horsemen. Later on, RoboCop, yes, the RoboCop, came out and bent the bars on the cage, allowing Sting to escape. There was never any mention of this again and RoboCop left just as quickly has he had arrived.
WCW had a strange one that actually lasted a few months. In 1998 during Nitro and Thunder the lights would flicker and an Evil Laugh would be heard. Most assumed it was a buildup for a new wrestler until the whole thing reached its conclusion when Rick Steiner was doing an in-ring interview with Mean Gene Okerlund, only to be interrupted by the evil laughter, who was then revealed to be (we are not making this up) Chucky. The evil possessed doll star of the Child's Play movies appeared on the video wall and made some jokes at Rick Steiner's expense for a while, while Steiner actually challenged Chucky to come to the ring and face him. Chucky did a plug for his new movie, Bride of Chucky, and then told Rick Steiner not to mess with Scott Steiner (who Rick was feuding with at the time) because Chucky wanted to direct him in a new film. This was, however, Chucky's only appearance in WCW, and the whole thing was never mentioned again afterward.
On the September 28, 2007 episode of WWE SmackDown!, accomplished indy wrestler Krissy Vaine made her on-screen debut by attacking Torrie Wilson after she had lost her match with Victoria. Vaine was seen negotiating with SmackDown General Manager Vickie Guerrero. However, Vaine, real name Kristin Eubanks, left WWE soon after, due to family health issues, and never returned. The attack was never referenced again.
In December 2008, in the middle of a backstage segment on Smackdown, the camera suddenly cut away to a new wrestler standing in a dark alley. The wrestler discussed how he has lived in darkness his whole life and how he has searched for followers for over a decade. He ended the promo saying that the prophecy would be realized, and that he would destroy a certain superstar who would live on with him being the vessel. The original plan was for the wrestler, named Hade Vansen, to feud with The Undertaker. However, after the first promo aired, WWE decided he wasn't ready to be called up, and moved him back to developmental, where he was fired two weeks later. The promo was never mentioned again.
On the December 21st 2009 edition of Raw, WWE apparently decided it was time for them to finally make a joke about Tiger Woods and his crumbling personal life. Unfortunately, they chose the worst way to do it: during the show's opening segment, while the guest host was cutting a promo, they had someone in a tiger mascot costume run out of the crowd with a blond woman chasing after him with a golf club (the two were also in a backstage skit an hour or so later). No reason was given for this, the announcers didn't really make a point of mentioning it, and felt so out of place with the rest of the show that it was pretty much a BLAM no matter how you look at it.
Probably the funniest example ever in pro wrestling occurred during the 2004 Royal Rumble. Midway through the match, right after Chris Benoit and Randy Orton (the first two entrants) had managed to eliminate everyone else in the ring, they temporarily knocked each other out and the match essentially came to a standstill. That's when a diminutive fellow in a tuxedo and an Afro wig came running out with a microphone and announced: "Ladies and gentlemen — Ernest 'The Cat' Miller!" Miller then came down to the ring as an official entrant — but instead of eliminating Benoit or Orton, or both, he and the diminutive emcee began doing a ridiculous dance in the middle of the ring to the tune of the Motown-esque song "Somebody Call My Mama." Even Tazz (who was commentating) thought it was hilarious, and started singing along! Oh, and did I mention that Miller was wearing a white cape and platform shoes? Needless to say, when Benoit and Orton finally woke up, they didn't find the segment at all entertaining; Benoit then tossed out the emcee while Orton eliminated Miller. The match then pretty much restarted without further incident. (Someone on Youtube appropriately referred to this as the "Royal Rumble intermission.")
That generally happens in a Rumble where there are early entrants who dominate most of the match like that, as a way to let them rest. In the 2001 Rumble, Kane entered at seven and was the last man over, at one point eliminating the entire ring single-handedly. So the next person to come out was old-timer Honky Tonk Man, who did something similar: had the audience participate in singing his theme song. After two minutes (exactly!) Kane beat him with his own guitar and eliminated him. The next entrant was The Rock, who stayed for the rest of the Rumble almost, so it was definately just to let Kane rest before having an epic battle with Rocky. Still BLAM.
How about the 2002 Royal Rumble when the Godfather made his return after being away for monthsnote The Right to Censor gimmick was progressively scrapped after WrestleMania XVII, with the Goodfather, Val Venis and Bull Buchanan being Put on a Bus to OVW prior to the big promotion-wide face turn leading up to the InVasion/(WCW/ECW)Alliance angle. by taking an overly long time to come to the ring while he danced with his Hos? It took him about two minutes to get to the ring...he didn't last long.
On the 4/19/2010 version of RAW, there was a promotional spot cross-promoting the movie MacGruber. To help with the bit, Ron "R-Truth" Killings was up at the start of the entrance ramp, drawing a reaction from the crowd, when suddenly...R-Truth disappears in an explosion set up by MacGruber earlier. Only his smoldering shoes are left. The whole thing is Played for Laughs. The next night on NXT, R-Truth shows up right as rain. No mention of it is mentioned ever again.
On TV. Killings was dropped from the week's Power 25 for it. 
"The rapping Superstar is off the P25 after being blown up by MacGruber on Raw."
In 2004, on WWE Raw, a video aired just before the main event of the show. It detailed the involvement of Japan in World War II, culminating in the bombing of Hiroshima and Nagasaki. The promo then said that a man was coming to WWE Raw to take revenge on the US for not only the bombing, but for the entire war and all the lives lost. The video ended with a man saying "Mark the return of Hirohito", and the word "Hirohito" being splattered on the screen in blood. The video was never mentioned or heard from again, the entire Hirohito gimmick was dropped, and the wrestler who was going to play him (Japanese star Kenzo Suzuki) ended up on Smackdown under his real name.
Of course, the reason the Hirohito gimmick was dropped is because someone thought-and I know this sounds crazy-that a guy running around pretending to be the emperor of Japan during World War II might offend some people and/or be irrelevant in 2004 (particularly since the actual Hirohito died 15 years earlier).
It was Hiroko Suzuki, Kenzo's wife, who apparently clued in creative that that Japan's not all that "seething with rage about WWII". The man who came up with such crap (along with Mordecai) was canned.
At ''SummerSlam 2009'', Randy Orton and John Cena faced off in a match that was restarted three times after increasingly illogical non-finishes. The third time the match was restarted, Cena quickly got Orton in the STF... then Ted DiBiase Jr.'s brother ran in from the crowd, broke it up, and took off allowing Orton to get the win. The next night Orton started Raw by confirming it was indeed Ted's brother... then the entire subject (including the multiple restarts) was dropped entirely and not brought up any further in the Cena / Orton feud that continued for months afterward. DiBiase's brother hasn't been seen since, either.
The November 1, 2010 edition of Raw — the day before Election Day — featured a segment in which, after many weeks of not seeing Vince McMahon on TV, he appeared asleep in a hospital bed with Freddie Prinze Jr. standing next to him, dressed in a doctor's outfit. Prinze commented on Linda McMahon's electoral campaign and how much money she spent on it, at which point Vince awoke from his coma, covered in Linda campaign stickers. He commented, "I hate politics" and asked Prinze if everything was okay in WWE. Prinze recounted several recent storylines — such as Undertaker being buried and Nexus's reign of terror — and Vince felt sick and had to go to the bathroom. Then he announced he would run for president, before standing up and apparently preparing to poop; a banner with the name of Linda's political opponent covered his butt. THEN, it cut to Stephanie McMahon waking up in bed and talking about how she had "the most horrible dream" where her dad woke up from his coma and announced he was running for president. Offscreen, Triple H reassured her "No, I'm pretty sure he's brain-dead." She responded, "Thank God." and the segment ended. The rest of the show continued as if absolutely nothing had happened.
Made even funnier by the fact that Vince was on TV the past couple weeks in pre-taped vignettes promoting the Stand Up for WWE movement.
On the 4/2/2010 edition of Smackdown, Kane decided that he was bored and would take on all 8 of the Season 1 NXT rookies by himself in an elimination match. Kane would prove dominant and score a few eliminations, until the remaning rookies got together and ganged up on Kane and beat him down handily, even though they ended up getting D Qed for ignoring the ref's 5 count. Aside from Kane making a couple appearances on NXT, this was never mentioned again. However, this would not be the last time that the NXT rookies teamed up, so it may have been subtle Foreshadowing.
In one episode of Raw, there's a brief segment where Derrick Bateman is promoting a WSM perfume, Mark Henry does a vo of the consequences of the perfume, and it's not at all talked about whatsoever for the rest of the show.
It was a rib on Mark Henry (who was trying very hard not to laugh while doing the voiceover), as he's apparently the stinkiest sweaty guy in the company.
When The Corre was having some internal disputes, Santino Marella suddenly shows up with his own Power Stable consisting of himself, Evan Bourne, Mark Henry, and Daniel Bryan. He introduces his stable as "APPLE," short for "Allied People Powered (by) Loathing Everything (that you stand for)". They lose uneventfully to the Corre in a 4v4 tag team match, and the group hasn't been mentioned by the WWE or any of the wrestlers involved since.
Santino is pretty much the resident Plucky Comic Relief, and tends to be the source of everything nonsensical and random. That said, the APPLE team-up may have also been a vague Call Back to the Corporation angle, when Mankind assembled the "Union of People You Oughtta Respect, Son!", a rough assembly of people who had been attacked or generally screwed over by Shane McMahon's group. It consisted of him, Test, Ken Shamrock and The Big Show, and after the introduction he stopped, counted on his fingers, and figured out the initials worked out to "UP YOuRS!" The Union feuded with the Corporation for about a month until Mankind (the only top-lister at the time) was injured and the confusing Corporate Ministry angle started, after which the Union evaporated, almost making it a month-long Bizarro Episode of its own.
One the June 20, 2011 episode of Raw, after the Capital Punishment PPV, R-truth comes out, and whines about how he got "Okey Doked" by Little Jimmy, where one of the kid fans in the front row at the PPV threw water in his face and cost R-Truth his WWE title match with John Cena. Christian, fresh off his 3rd lost against Randy Orton and heel turn comes out and whines about how he has been screwed by the fans, who voted on Friday Night SD after after Christian won his first WHC, to face Randy Orton in a title match, in which he lost. The Miz comes out, whining about how he has been humiliated by his former apprentice Alex Riley and how he lost to Riley at Capital Punishment. This all turns into the three them in a most humorous way antagonizing eachother on their past transgressions.
On the July 4, 2011 episode of Raw, WWE Tag Team Champions David Otunga and Michael McGillicutty are celebrating a victory over Santino Marella and Vladimir Kozlov when out comes Zack Ryder of all people. Ryder recites his Catchphrase ... and RAW cuts to a commercial and the interruption is not mentioned on the show again. It's odd because this is literally the second time that Ryder has appeared in front of a live audience on RAW this entire year. One could construe this as a challenge for the Tag Team titles, but Ryder didn't bring a partner with him and his tag team with Primo was disbanded off camera a few weeks ago on Superstars so Ryder could wrestle Primo in front of his Long Island hometown crowd. Perhaps WWE management finally listened to the cult following that his Internet show Z! True Long Island Story has garnered and decided to throw them a bone with a non-sensical cameo.
The May 10, 2010 episode of Raw had Randy Orton interrupted by Meat Loaf of all people, who tried to convince Orton to use one of the songs from his new album as his theme song only to get RKO'd, never to be seen again. To add to the randomness of the segment, this was during the Guest Host period of Raw and Meat Loaf wasn't even the Guest Host of the night, Flavor Flav was.
The point was to (somewhat redundantly) make clear that Orton was out of control and would RKO literally anyone who got in the ring with him (despite being a face by this point!) for no reason. Edge at least made reference to the incident elliptically, saying that he was sick of Orton RKO'ing random people all the time.
Throughout much of the late 1990s, the WWF had pretty much a series of BLAMs. They all involved a black and white hidden camera segment of sorts showing wrestlers and managers backstage, that often times would lead to pretty much nowhere. The segments were originally called "GDTV" but the name was later changed to simply "GTV." No explanation was ever given to, well, anything about these hidden camera segments. Not who was behind them, not what the name stood for (or even why it was changed), nothing. They were originally intended as promos for the return of Goldust. When he requested his release from the company, they kept running under the GTV name for a while. Presumably they were meant to be attached to someone else but were eventually abandoned.
The GTV segments did indeed lead to something, though most likely not what the original idea was meant for. During an angle which saw Chaz (Mosh from the Headbangers) constantly being accused of abusing his girlfriend Marianna, Chaz's former partner, Thrasher, came out during one of these moments and revealed a GTV segment that caught Marianna on camera applying makeup to look beaten and bruised. Marianna was then arrested, and Thrasher and Mosh reunited as the Headbangers for a short and uneventful run.
Beth Phoenix tends to bring these out in her opponents. One absolutely random (and we mean random) moment came in a match against Eve Torres at Vengeance where Eve used Beth's own outfit to hogtie her to the ropes so she could kick her in the ass.
Layla seemed to take exception to Beth saying "you can't even lace my boots" at No Way Out and so stole Beth's headband and started playing it with, then doing the "Single Ladies" dance.
Another one happened during Raw Roulette, where when he was spinning the wheel, Edge starting fistpumping and singing Flo Rida's Right Round with Jillian Hall, only to stop and give her a weird look.