Most of us English-speakers were told as children that it’s wrong to say me and him went to the park, and we should instead say he and I. And many of us grow up extending the lesson to where it does not belong: the letter was addressed to she and I. Purists like me expostulate in vain: one wouldn’t say or to she or to I, or indeed to we, so why to she and I?
It now hits me that, in all these years of wincing at between he and I, I’ve never asked why children make the opposite error. Children rarely if ever say me went or him went, so why was it so much more natural to say me and him went?
Perhaps in all of these phenomena the partnership is considered a new entity, distinct from its components. So now I’m inspired to ask: In languages that still have a strong case system, e.g. Russian, what is the genitive of a company name like Sears & Roebuck? Do both elements become genitive, or only the last, or is the whole thing indeclinable, or what?
I have no way to speak about Russian, but only, as you know, about Portuguese, which doesn’t have that strong a case system.
In Portuguese we have a vice about expressions like: “He asked me to answer that”. We would say: “Ele pediu para eu responder isso”. People will mix that with “He asked me”, which translates to “Ele pediu para mim”, and we would have something like “Ele pediu para mim responder isso”. It is kind of like “me went”, but only for phrases with more than one verb, and it is a common mistake.
And what about the expression “you and me” as opposed to “you and I”? For someone not thinking about the details of the language, the rule that sometimes you say “you and me” and sometimes you say “you and I” is probably very confusing. At a time it confused me, because I started thinking that English was not very logical if it required me to say “you and me went to the movies”, as at a time I thought it did.