From 30 Rock:
Tracy Jordan, insane actor: Hey, boy. How are you doing?
Toofer, Harvard-educated comedy writer: I’m doing good.
Tracy Jordan, insane actor: No, you’re not, idiot! Superman does good. You do well. You gotta start taking care with your English, son!
30 Rock is the best, funniest and most unjustly ignored show on TV. Click here to buy the DVD on Amazon.com (well worth it) or click here to watch an episode for free. You can also watch the first season on demand via Netflix!
The Grammar Vandal 
I think “doing” is a copula in this instance.
I wonder if this isn’t one of those things we should just accept as a part of our changing language. I hear so many d-bags at my job saying “I’m well” i could scream.
Good is recognized as an adverb.
From Merriam-Webster:
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Main Entry: good
Function: adverb
Date: 13th century
1 : well (he showed me how good I was doing — Herbert Gold)
2 —used as an intensive (a good long time)
Usage: Adverbial good has been under attack from the schoolroom since the 19th century. Insistence on well rather than good has resulted in a split in connotation: well is standard, neutral, and colorless, while good is emotionally charged and emphatic. This makes good the adverb of choice in sports (“I’m seeing the ball real good” is what you hear — Roger Angell). In such contexts as (listen up. And listen good— Alex Karras) (lets fly with his tomatoes before they can flee. He gets Clarence good— Charles Dickinson) good cannot be adequately replaced by well. Adverbial good is primarily a spoken form; in writing it occurs in reported and fictional speech and in generally familiar or informal contexts.
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Dictionary.com also recognizes “good” as an informal “well”.
When Toofer says he is doing good, the context eliminates any ambiguity. Tracy asks “how” Toofer is doing and not “what” he is doing; therefore, it is clear that Toofer does not mean he is doing meritorious works, but that he is in a state of well-being.
I’m a big sitcom fan, but I’ll admit to never watching 30 Rock. It’s odd, because it’s on between Earl and The Office, both of which I watch every week.
I think it’s because I never “got” Tracy Morgan. I don’t think he’s funny and I don’t see what the fuss is about. He strikes me as one of those guys who just wandered into something.
Anthony, I agree about Tracy Morgan — though I loved his Brian Fellow character on SNL, he’s not really my cup of tea. And, to be honest, it takes a bit of time to warm up to him on the show.
But with Tiny Fey and the incredible Alec Baldwin (this is the role he was born to play!) leading the stellar cast, you will grow to love Tracy Jordan and his antics!
That’s interesting about the adverbial “good”.
It bothers me when people get riled up about “being good” or “doing good” because I’ve never understand why “good” could not be used as a subjective complement / predicate adjective.
You might be happy to learn, as I was while reading the Boston Sunday Globe this weekend, that March 5th is National Grammar Day. Unfortunately, it is not National GOOD Grammar Day, so I fear it will likely be a day just like every other……