NOTE: This spoiler was written by L.
In Eastern Siberia, a group of terrorists seize control of an X-5 missile. Led by Deter von Cunth (Val Kilmer), they smuggle the missile into the United States in order to make millions through their acts of terrorism. Colonel Jim Faith (Powers Boothe) and Lt. Dixon Piper (Ryan Phillippe) catch wind of the theft and go to Ecuador to find their best man: MacGruber (Will Forte).
MacGruber has been “dead” for 10 years and been meditating in an Ecuadorian church. Faith and Piper try to convince him to return to duty. MacGruber takes a disliking to Piper, despite Piper’s admiration for MacGruber’s exploits. MacGruber retired from active duty when Cunth killed his bride, Casey (Maya Rudolph), during their wedding with a bomb. Colonel Faith tells MacGruber that Cunth is behind the attack. MacGruber turns Faith down but has a nightmare of Casey’s murder. He goes to her grave and digs out his own coffin which has his trademark MacGruber uniform. In the rain, he gets dressed and cuts his hair into a mullet, ready to hunt down Cunth.
Colonel Faith suggests that MacGruber take Piper onto his team, but MacGruber wants to make his own team without Piper. He head butts Piper and goes off to make his team. He picks up a group of tough guys and takes them back to the Pentagon (making a point to not bring his homosexual teammate along). He tries to recruit Vicki St. Elmo (Kristen Wiig) but Vicki, now a musician, turns MacGruber down despite her obvious feelings for her. He gives her a note written in a child’s scrawl which tells her she can find him in the Pentagon. With his team assembled, he briefs Colonel Faith on his plan but Colonel Faith asks him where his men are. MacGruber tells him that his men are in the van with his homemade C4, just before the van explodes, killing all of MacGruber’s men.
After their hasty funerals, Colonel Faith tells MacGruber he’s off the case. MacGruber is devastated and Faith leaves him in the Colonel’s office. Piper enters a few minutes later and MacGruber begs Piper to help him. MacGruber gets on his knees and tells Piper that he’ll suck his dick or let him fuck him if Piper agrees to join the team. As MacGruber sobs “tell me what you want me to fuck” and takes his pants off, Piper agrees hastily just as Faith walks into the room. Faith tells MacGruber that two people aren’t a team. Vicki arrives and offers to join after hearing about what happened. With his team assembled, the crew goes off to Las Vegas.
MacGruber takes his team to Cunth’s casino in order to deliver a message. As he’s driving, an asshole in a silver car mocks MacGruber’s car. MacGruber memorizes the license plate number and swears revenge (KFBR392). MacGruber enters the casino and enters the night club portion. He causes a ruckus and screams into a mic while taking Vicki “hostage.” He then tells Cunth’s cameras and guards where they can find him tomorrow and leaves. Piper tells MacGruber that he’s taken away their only advantage (Cunth thinking that MacGruber was dead).
Cunth is in his house painting a picture of an old naked woman when his men show him pictures of MacGruber in the club delivering his message. Cunth tells them not to underestimate MacGruber and order him to kill MacGruber.
During their sting operation, MacGruber has Vicki pretend to be him in a local café. After awkwardly coaching Vicki on what to do via earpiece, Piper and MacGruber’s van (20 blocks away since MacGruber didn’t want to pay any parking meters) is attacked by Has Bender, one of the terrorists. While Vicki enacts MacGruber’s screaming and crying on the floor of the café, MacGruber uses a makeshift mop to hit the gas pedal and kill Bender with his car. With the threat neutralized, Vicki awkwardly gets up and leaves the café.
The trio find Bender’s car and see it’s full of money. Piper deduces that Bender is going to buy the pass codes for the X-5 missile. They find the deal’s location from Bender’s GPS and find it guarded by three men. MacGruber distracts them by sticking a piece of celery in his ass and waddling around naked like a duck. Piper is horrified, as are the guards, but takes the opportunity to shoot them dead. They dress Vicki up like Bender but she is immediately compromised and shot at. She runs away and Cunth’s surviving men take the money. Piper kills the Chinese man with the pass codes but they steal the suitcase and run. After the raid, MacGruber is eating celery (He washed it! ...No, he didn’t.) when the Colonel calls. He tells MacGruber that Cunth is having a party at his house. He tells MacGruber to observe but NOT to enter the party…and is promptly ignored.
MacGruber crashes the party and walks in on Cunth playing poker with a US Senator. MacGruber tells the Senator that Cunth is bluffing and the Senator goes all in. Cunth wins with a straight and the Senator loses everything. Cunth and MacGruber have a faceoff but MacGruber is quickly thrown out of the event. Vicki notices the Senator being given an envelope with instructions and told to “do it for the sake of your family.” After MacGruber is brought before Colonel Faith and Colonel Faith tells him the mission is over. MacGruber offers to suck his dick, but Faith insists it’s over.
The trio returns to MacGruber’s trailer. They share a beer until Vicki decides to use the bathroom. Piper asks why MacGruber isn’t trying to get with Vicki but MacGruber explains that he hasn’t been with another woman since Cunth killed his wife. He tells Piper the story: MacGruber, Casey and Cunth went to college together. Casey was engaged to Cunth before MacGruber started banging her. She left Cunth but was pregnant with his child. MacGruber insisted she terminate the kid so that they’d get a “fresh start.” (yes. He says all this.) MacGruber hears assassins ready to pounce and uses Piper as a human shield before grabbing Vicki and getting in his car. As they drive away Piper asks how MacGruber knew he was wearing a bullet proof vest. MacGruber pretends he knew but Piper gets pissed and demands to be dropped off.
MacGruber takes Vicki home and she notices that he was shot in the leg. She takes the bullet out, which turns MacGruber on. He deflowers her and then abruptly leaves, guilty of over having cheated on the memory of Casey. He goes to her grave and imagines her spirit there. She absolves him of guilt and they have sex. A grave keeper sees MacGruber fucking air but to him it’s as if he’s having sex with Casey. Once he’s done he decides to go back to Vicki’s but sees the car from Vegas: KFBR392. He goes to town on the car, breaking its windows and lighting it on fire. The owner freaks and MacGruber tells him to go fuck himself. He gets a call from Colonel Faith who says he got Intel which proves that Cunth was not behind the theft. MacGruber calls bullshit and goes to Vicki’s. Colonel Faith asks the Senator (his source) how reliable the intel is, but is quickly shot by the Senator. Her place has been ransacked. He gets a call from Cunth but cunningly uses flattery to buy time and trace the call, locating Cunth’s compound.
MacGruber meets up with Piper and they go to stop Cunth. MacGruber impresses/disgusts Piper by ripping out the throats of his opponents. He obtains a “turkey” (three consecutive throat rips). When they break into the control room they kill the guard and desecrate his body to pull a prank on the goons. They get cornered in a boiler room and Piper gives MacGruber a gun. MacGruber confesses that he never uses one because he doesn’t know how. MacGruber just points and shoots wildly to scare the goons while Piper uses his gun to make more precise kills. MacGruber redeems himself by moving to take a bullet for Piper but the henchman’s gun jams. Unfortunately, they are captured when they go to rescue Vicki.
The trio is brought before Cunth and the X-5 missile. MacGruber vows to rip off Cunth’s dick and shove it down his throat but Cunth says that soon he will blow up Washington with a nuclear bomb and be rewarded handsomely by the Chinese. The trio fights back and they kill Cunth’s henchmen. With 3 minutes before launch, MacGruber manages to handcuff Cunth to a pole. MacGruber starts getting distracted by his personal issues (asking Vicki to marry him) and is shocked by the arming mechanism of the bomb. He realizes that he can’t defuse it since it has too many wires and Cunth gloats that even though they’ll die, he still wins. MacGruber then rips out the thermonuclear core and the guidance system of the missile, effectively neutralizing its capacity to fly to Washington. With 32 seconds to spare, the trio escapes and leaves Cunth to die. However, before the explosion, Cunth notices an axe within reach…
At MacGruber and Vicki’s wedding day, the pair are about to finalize their marriage and say their “I Do”s when MacGruber gets a chill. He sees a horribly disfigured Cunth in the distance and pulls Vicki down just as Cunth fires his bazooka (killing the priest). MacGruber fights Cunth and brutally beats him. He pulls out a knife and goes to cut off Cunth’s dick but Cunth laughs and tells him that he lost his penis in the explosion. MacGruber gets pissed and decides to settle for throwing Cunth off a cliff, shooting him repeatedly, lighting him on fire and then pissing on his corpse (and subsequently a shit in the after credit photos). Once he’s done, he turns to Vicki and says “I Do.”