There are 2 forms of pronouns:
- subject form: I, you, he, she, it, we, they
- object form: me, you, him, her, it, us, them
These 2 forms are not interchangeable. - Wrong: My sister and me wanted to take a hike! - Right: My sister and I wanted to take a hike! - Wrong: Mike ran after Jack and she. - Right: Mike ran after Jack and her.
And there are some rules on where to use which form:
- Use subject form: after to be verbs. E.g. It is I. It was they. It is she.
- Use subject form: after than and as. E.g. Chuck is taller than I (am). Dolphins are known to be smart as they (are).