Keep in mind -- those couples lines of action aren't REALLY the characters' introduction.

What is Melvin's introduction? He's trying to shove a pug down a garbage shoot.

What is The Dude's? He's drinking milk out of a carton in the grocery store and then pays 69 cents for it with a check.

Now -- THOSE are character introductions. When people are talking about character introductions... that's what they mean.

Not the 2 - 4 line description of the character. You can almost put anything in those lines.

The question I was addressing in class was specifically about the scene description aspect of introducing a character. Hence, the focus of my post. But your point is taken: a character's introductory actions can certainly help cement that character's persona / identity in a reader's mind.

Yeah, I know. I just think the couple lines of description pale in comparison to how the audience really meets the character onscreen for the first time.

Those lines of description are more a factor of writer's voice than anything else. If it's not an interesting, memorable scene in which we first meet the character it's easy to lose/forget even the 4 best lines of prose in a 100 - 120 page document.

It's much easier to remember, the dude that pays for 69 cents worth of milk with a check. The guy shoving a pug down a garbage shoot.