"It is an excellent couple"? Not "it" but "they are" surely, as a pair, i.e. two, make a couple. We just wouldn't say "it is an excellent couple" in English. It sounds wrong, at least to my ears. As for "that is an excellent couple" there was no sense of that in the Portuguese sentence, either, esse or aquele.
I believe "casal", as its relationship to the word "casar" (to marry) makes clear, is usually associated with a courting or married couple [Edit: that's not correct it seems - see Ruama's comment]. A couple of things can be described using "(um) par". Probably the best word for your example is "combinação" (combination).
Ah, but mashed potatoes and carrots aren't lovers, that's boiled beef and carrots. :-)
Yes you can use "it" for a couple. "They" is most common and refers to two people working well together as a couple. "It" can be used when you refer to a couple as a single whole, though you're more likely to use "this is". "Do you see the Smiths over there? It is an excellent couple to observe as an example to others!". "I present to you the Smiths. This is the couple that made me believe in everlasting love being possible".
Inshadeone, where do you live that using it to describe a couple in the context you did would be acceptable? Everywhere I have been the correct conversation would be "Do you see the Smiths over there? They are an excellent couple to observe as an example to others!" I would like to know where in the world your example is considered correct?
I believe it's wrong, unless you turn it into something like "you (two)
make an excellent couple".
- (você) é excelente casal (but a single person does not make a couple)
sãoexcelente casal (with são and also with a plural for a group which is not correct unlike in [British] English)