Bruce Lee was the martial arts adviser for this film. He also was brought in to train and teach Sharon Tate with her martial arts scenes.

Film debut (as an extra) of Chuck Norris

Dean Martin was so distraught over the murder of his The Wrecking Crew (1968) co-star and friend Sharon Tate in August 1969, six months after the movie was released, then still playing in theatres in the US and opening internationally, that he abandoned the next already announced "Matt Helm" motion picture series installment (to be titled "The Ravagers") and never played the character again. This is contrary to the widely held opinion that the series ended due to poor reviews and box office.

Exteriors at 141 S. Carolwood Drive in Holmby Hills were used for the chateau owned by the Count Contini character. Built in 1936 the estate was known as 'Owlwood'. Co-founder of 20th Century Fox Studios 'Joseph Schenck', Tony Curtis and Sonny Bono & his then wife Cher are some of the famous people who have owned the estate over the years. At the time 'The Wrecking Crew' was made the place was owned by Tony Curtis who was friends with Dean Martin and Sharon Tate both of whom starred in the film.

In the closing credits as had been done with prior Matt Helm films, the next Helm film was announced, titled The Ravagers. That film was never made. The Wrecking Crew was the last of the Helm films.

Continuity

While Dean Martin & Sharon Tate are flying in the helicopter, they swap seats at one point.

Although the two cars hit side to side several times on the mountain road, there is no visible damage to either car.

After another car tries to run Matt helm's Lincoln off a mountain road and denting in his driver side door, the door is miraculously fixed with no dent as Matt continues to drive it and gets a way.



Factual errors

A billion dollars in gold is exponentially more than would fit on a single train car which has a max weight of less than a couple hundred tons.

After the car is damaged at the creek Matt and Freya take two duffel bags out of the trunk and put together the helicopter. There is no way two duffel bags can hold all the parts to make the helicopter. Also, even if the engine was in one of the duffel bags it would have been too heavy for Matt to have taken it out of the trunk using just muscle power.

The villain Wen Yu-Rang and her gang appear to be Chinese however the wise cracks include references to the yen and a kimono.



Revealing mistakes

In the final fight scene on the train, a trap door opens up on the floor of the locomotive and we see the ground beneath rush by. However, no railroad ties are visible. The "ground" is very likely just a treadmill belt.

After Matt and Freya are in bed and accidentally trip the emergency brake on the train, they are thrown out of bed towards the camera. The wires suspending them are visible.

It is clear that in many close-up shots, there is no windshield in Matt's Lincoln.



Miscellaneous

In the fight between You-Rang and Freya, none of the blows or kicks actually connect. Each fighter can be seen to grab at a body part that has been struck, when the blow was seen to be aimed at a different part.

While Dean Martin & Sharon Tate are flying in the helicopter chasing a train, the shadow of a very different helicopter is visible in the background.



Anachronisms

Nixon didn't assume office until January of 69. Film was released in Canada in December of 68.



Crew or equipment visible

After throwing one of his 'grenades', Matt Helm leaps over a hedge and lands on a lawn which is a stunt mat that ripples as he moves on it.

The people in the helicopter when it lands at Contini's estate are obvious doubles for Dean Martin and Sharon Tate.



Errors in geography

There are no mountains in Denmark