...Norwegians learn Norwegian; the Greeks are taught their Greek.(See here from 2:17 on.)
An entry in which nwhyte may be Taking It All Too Seriously.
I have been wondering a bit about this line. Of course, the main reason Lerner and Lowe chose Norwegian and Greek as the two examples must have been rhythm and rhyme. There are not a lot of alternatives. Other languages with more speakers than Norwegian, whose names both describe the people who speak them and are pronounced as amphibrachs include "Bengali", "Korean", "Somali", but I guess that "Norwegian" fits the cultural context of "My Fair Lady" better. (You could also consider "Ukrainian", "Romanian", "Hungarian", "Albanian", "Bulgarian", "Armenian" and "Mongolian", but a lot of people would pronounce them with four syllables, while I think most English speakers would elide the "i" in "Norwegian".) And the only other language I can think of which would rhyme with "speak" is "Creek". (One could stretch a point for "Arab-eek" or "Amhar-eek", or with a bit more geographical outreach "Tajik", but "Greek" is an understandable choice.)
But the interesting thing about the line "Norwegians learn Norwegian; the Greeks are taught their Greek" is that in 1956, when the musical of My Fair Lady was made, and in 1964, when the film came out, it was not true. At least, not completely. Both Greece (at the time) and Norway are classic examples of countries in a state of diglossia, where there were actually two versions of the official language. Anyone learning Norwegian even today must choose between Bokmål and Nynorsk (Bokmål is a bit like Danish; Nynorsk is a bit like Bokmål). And until 1974, anyone learning modern Greek had to choose between the nineteenth-century Καθαρεύουσα and the (literally) demotic δημοτική (which is now the only standard). It is ironic that the two languages Lerner and Lowe chose for Professor Higgins' line are the two European languages of which the statement was least accurate at the time they were writing.
I strongly suspect Lerner and Lowe were unaware of this wrinkle. More likely, if there is another reason, they chose Norwegian as a mild homage to Ibsen, whose dramatic influence on Shaw is well attested, and Greek as a reference to the original source of the Pygmalion myth which Shaw drew on for the plot and title of his play.