The "antique" spectacles that Kirk sells to the antiques dealer when they first arrive in San Francisco are described as 18th century. After telling Kirk how much he will pay for them the dealer says they would have been worth more if the lenses were intact. The glasses have plastic ear pieces which they most certainly wouldn't have had in the 18th century and you can also tell that they do have lenses in them.
When Scotty is typing on the computer in the plexiglass factory and his hands are shown, the sound effects of typing do not match up with his hands, which are moving much slower. In addition, there is no way a single keystroke as demonstrated by Scotty could create the level of graphics shown on the 1986-vintage Macintosh computer used in the scene.
When Spock tells Gillian that Gracie is pregnant, she brakes the truck and we hear a squealing sound indicating that the tires have locked-up and are skidding on the road. However, the scene immediately cuts to a side shot of the truck stopping and the wheels are not locked - the truck comes to a gentle stop.
Before the attempt to return to the 23rd century, Spock says that his calculations will not be completely accurate as Scotty is unable to give him a precise value for the mass of the whales and the water. Yet the transporter would be able to give a very precise measurement of the mass Scott had transported, down to the atom.
When Kirk and the crew first exit the ship after landing in Golden Gate Park, Uhura says the whales are on a heading of 283 degrees (Spock repeats this heading at the bus stop). 283 degrees from Golden Gate Park heads straight out to sea without passing near Sausalito.
When Dr. Taylor drops off Spock at the park, the ignition switch of the Chevy pickup is shown in the "off" position, yet engine idling sound continues and there is no sound of the engine starting up again.
As the Bounty starts going to warp for time travel, we see Spock's hand-held display fall off the console to the desk, and there's a close up of it landing. A long-shot of the bridge, including the area in front of Spock's console doesn't show the hand-held.
Right after the Bounty has landed in the park and the trash men start to flee, some of the trash cans nearest the truck are full to or nearly to the tops. But as the truck drives off, those cans appear to be empty.
During Dr. Taylor's conversation with Kirk and Spock in the pickup truck, three women (dressed in pink, purple, and denim) are briefly seen through the passenger-side window walking along. Thirty seconds later, the same three women are seen through the driver-side window, walking in the opposite direction.
After Spock nerve pinches the punk, the punk's head falls on the radio and probably hits the off switch, killing the music. Kirk resumes normal speech, but Spock is still speaking louder than necessary.
When Sulu accidentally turns on the windshield wipers of the helicopter, the wipers were broken so a grip had to move the wipers manually. Look closely and you can see his finger holding on to the blade as it moves back and forth.
Just before Spock checks the bus map at a stop, you can see several crew members are visible through a large glass window of a restaurant - one of them even clearly wears a "Star Trek IV" security badge, and all are wearing walkie-talkies.
Kirk and Spock are seen walking as Dr. Taylor drives up. She asks where they are going, Kirk replies "Back to San Francisco." The scene is shot in the Marina District of San Francisco. Kirk and Spock are already in San Francisco, Sausalito is on the other side of the Golden Gate Bridge which is behind them. While it is possible that Kirk may simply made a mistake being from the future, Dr. Taylor later even mocks him at dinner saying that they couldn't even get back to San Francisco without a lift.
When Dr. Gillian Taylor picks up Kirk and Spock while they are walking into San Francisco, you can clearly see that the street is actually a parking lot. The stall markers are on still on the pavement.
Ships in the opening sequence that are affected by the probe lose power and come to an almost complete stop. In the vacuum of space, air friction does not exist, so they should keep going the same speed they were before.
When Kirk asks Scotty how long the transporter bay is, he replies, "About 60 feet." Other units of measure throughout the movies have characters using metric units (meters, kilometers, etc) so it seems much more likely that Scotty would have said, "About 18 meters."
The "On duty Commander" aboard the Enterprise Air Craft Carrier (i.e. U.S.S. Ranger CV-61) Stated, that their was an "Intruder in M.M.R. number 4". This is an questionable statement probably due to assumptions by some one not familiar with military terminology. M.M.R., possibly refers to "Main Missile Room" which at the time of this film (November 1986) did not exist except on paper. Though on the drawing boards was "Gerald Ford class (or Ford class, previously known as "CVN 21 class") which is a class of super-carriers currently being built to replace some of the United States Navy's existing Nimitz-class carriers." Designed originally in 1975. The first two ships, USS Gerald R Ford (CVN 78) and USS John F. Kennedy (CVN 79), will be commissioned in 2015 and 2019. The carrier(s) will be armed with the Raytheon evolved Sea Sparrow missile (ESSM), which defends against high-speed, highly maneuverable anti-ship missiles. This information most likely was classified "Top Secret" in 1986. CVN-80, U.S.S. Enterprise should be commissioned by 2025, She will be the ninth ship and the third aircraft carrier in the history of the United States Navy to bear the name. Trekkers rejoice! Magazine applies to any compartment, space, or locker that is used, or intended to be used, for the stowage of explosives or ammunition of any kind., also stowed separately from powder or fuel used to launch stated projectile(s) generally located below the main deck, and insofar as is practical, below the waterline.For safety reasons and only brought together during readiness for battle or defensive preparation(s).This is S.O.P. (Standard Operating Procedure) for many military branches. The "Big E, Grey Ghost" would not normally have had any nuclear weapons on board except in some form of transportation scenario. While a ship of the line might have defensive missiles on board as protection from airborne or surface enemy platforms. It is highly unlikely that the Enterprise would have a "Missile Room".
When the Bird of Prey is seem warping towards the Sun, the Sun is shown to glow with a pale yellow light, but in space, it would glow with a bright white light, since the Sun only appears yellow from Earth's perspective due to the atmosphere.scattering blue light.
When the tour group is viewing the whales from above and it it sprays water from it's blow hole there is a small amount of smoke (you can tell the difference from water spray by the way it drifts out) that trails out after the initial spray possibly from the charge used to propel the water from the prop whale blow hole.
When the elderly lady is being pushed in a wheelchair, happily saying, "The doctor gave me a pill and I grew a new kidney", the nurse on the left side of the screen almost trips over the wheelchair, but manages to recover.
When Spock is being tested by the computer, some camera angles are shot through the display screens. The text when viewed from the back is still displayed forward, which can be explained as a feature of a holographic alien device from the future rather than a goof.
Checkov states that the nuclear vessel they find is called the Enterprise. While it is actually the USS Ranger (CV-61), in this film the Ranger "plays" the Enterprise, much like an actor playing a part.
The goof items below may give away important plot points.
Immediately after the whales' transponders are located in the Bering Sea, Gillian can be seen to mouth "How did you do that?" without sound, then she is immediately seen and heard giving the same line from another camera angle.
After the trial in which Kirk is demoted from Admiral to Captain, the crew are shown in a shuttle craft heading for the Enterprise-A. If you look closer at Kirk's uniform, he is wearing the correct rank of captain, however he is still wearing the gold pin-striping on the front of his tunic (jacket) which is part of the admiral decoration. This was removed for Star Trek V: The Final Frontier and onward.
In the ending scene, following the "trial" Sarek and Spock are exchanging what amounts to Vulcan pleasantry. Spock says to Sarek, "Live Long and Prosper" Spock's father, Sarek, in response, repeats "Live long and Prosper, my son", however, in Vulcan tradition, the proper response would be "Peace and long life"
When the Bounty appears above the whaler, the whaler's helmsman begins spinning the wheel madly to starboard (the right). From a long shot, the whaler turns quickly. A closeup of the whaler's captain and helmsman doesn't show any movement. The sky and water behind them don't change.
When the Bounty uncloaks over the whaling ship, it's shadow can be seen over the ship in the wide shots, but in the closeups of the whaling ship, no shadow can be seen on the ship or the water around it.
At the end when the camera pans the crew just before their pardon, Scotty wears the rank pin of a Commander. This is despite his being promoted to Captain in Star Trek III: The Search for Spock, being listed in this film's credits as "Captain Montgomery Scott," and wearing Captain's pins in the next film, Star Trek V: The Final Frontier.
The Bounty is shown hovering above the whaler with the whaler deep in its shadow. When they cut back the bridge of the whaler, they're back in the sunshine. They cut back to show the Bounty hovering over the whaler, and it is once again in shadow.
When the Bounty is descending towards the whaling ship, there is a shot of the whales immediately following a quick shot of the harpoon. At the extreme right-hand side of the underwater whale shot you can make out a diver from waist up.
The first time Kirk and the crew boomerang around the Sun to achieve time travel, the ship nearly breaks apart, with things popping and exploding on the bridge. But the second time they do the same, it appears to be a relatively smooth ride. Apparently, the second time Spock managed to calculate the ship's trajectory better than the first time. In a previous scene Kirk teaches Spock to use human intuition in order to solve the return trajectory problem. Perhaps the intuitive approach had paid off.
After they all escape, Chekov's phaser is still in the possession of the military agents that had originally arrested him. While McCoy earlier in the film airs his concern to Scotty about leaving advanced technology (Plexiglas scene) or information of same in the past, no concern is given to Chekov's phaser, which is left behind.
The crew at Starfleet HQ in San Francisco shout and point, "There, There!" as to indicate the descent of the Bounty as Kirk and crew return through the clouds, yet the cloud cover is so thick that nothing past the bridge can be seen, so how could the Admiral see the ship, let alone know that it was coming?
When the Bounty appears above the whaler, the whaler's helmsman begins spinning the wheel madly to starboard (the right.) He continues spinning the wheel long after the wheel would have stopped as the rudder came up to the stops.