Yes there are, quality control was a bit lacking.
The most famous was the Bahamas Mule of 1967, this was a NZ 2 cent piece tails with a Bahama Islands Heads, it seems the Bahamian nickel and Kiwi coin were the same size, but of different metals (Nickel vs Bronze). Its not that rare ($100 or so and a few thousand)
In 1985 was also a 50 cent NZ tails with a $1 Canadian heads. The Nickel $1 Canadian coin was almost the same size as a NZ 50 cent piece. This coin is so rare that no sales are known and like the 1981 error probably only 1 - 5 in existence.
Another error was the 20 cent NZ coin of 1975 struck on a Hong Kong $2 planchet. This was the scalloped one which was debuted in 1975 (The $5 coin was a huge decagonal thing) and again this coin is incredibly rare.
Images credits (These sites own the images not me)
50 cent coin - icollector.com, numiscanada
Bahamas mule - australiancoins.com
Hong Kong $2 - the saleroom.com


