They’re not natural to me, and they sound pretty bad. I guess they sound natural to the people who say them. The same people say things like, “Her and I went to the party,” and, “Him and I are friends.”
Rather than say that they are ‘unnatural’, I would call them very informal. I would also add that these informal versions are not necessarily used by everyone (in AmE). I would say that there is probably a significant number of people who never use them.
Those versions are markers of social class and educational level. If you’re a native speaker and you say them, people will assume you have educational deficiencies. If you’re a native speaker and you write them, most people will assume you’re stupid. They’re about on the level of pronouncing “picture” and “pitcher” the same, in terms of the negative judgments they bring down on people. But they’re not as bad as saying “liberry”.
It’s stigmatized even in less formal settings, if people happen to be paying attention. Many of my friends come from Appalachian families and blue-collar Polish-American families, and even they consider that usage “low class”. It’s nearly as bad as saying “shoulda went”.
I always thought (and I am sure) that British (and American, and other English-speaking) people are extremely polite, attentive and well-brought-up. That’s why they put their friends’ names, or other people’s names first, then I. As for with you and Tim, we address this person, not Tim. And Tim doesn’t know whom we respect more.
No, library. Children have trouble pronouncing that word, and so they usually pronounce it as “liberry” [laibɛri], similar to “strawberry” or “blueberry”. Most people start pronouncing it correctly by the time they’re 7 years old, but if they never do, people take it as an indication that the person has a low educational or cultural level.
It’s what some people say instead of “should have gone”.
Note that among native English speakers – at all levels of education – “should have” is pronounced [ʃʊdə], “would have” is [wʊdə], and “could have” is [kʊdə]. This makes the conditional hard to hear, so a lot of ESL students who have been around native speakers for years will think at first that they’ve never heard the conditional.
Ho, ho, ho! If you only knew!
I think it’s more complex than that. I think with “you and Tim” the pronoun simply comes first, but we can put Tim first if we wish to give his name emphasis.