Alicia Silverstone -- and for the record, that's "ah-LEE-see-ya," not "ah-LEE-sha") -- is celebrating an anniversary this year. Twenty years ago, she went from a hottie teen boys lusted for (in "The Crush" and those Aerosmith music videos) to a funny hottie loved by millions in the iconic '90s film "Clueless."

These days, the California native, 38, is flexing her stage muscles, starring in "Of Good Stock," a new play by Melissa Ross, which opened Off-Broadway at the Manhattan Theatre Club's New York City Center on June 30. The comedy offers up Silverstone, Heather Lind and Jennifer Mudge as the dysfunctional Stockton sisters, offspring of a famed novelist, who return home to Cape Cod with their significant others . . . and lots of baggage (the emotional kind, of course).

When she's not acting, Silverstone lives what she calls "the kind life" -- a healthy and environmentally aware lifestyle championed in her bestselling books ("The Kind Diet," "The Kind Mama") and website ( Married with one son, named Bear, she recently spoke with Newsday contributor Joseph V. Amodio.

It must be fun playing one of a trio of bickering sisters.

The play is hilarious. You'll certainly laugh and you may very well cry. Most people do. It's so juicy, what we get to fight about. We're having such fun together -- aside from the first week of previews, which was absolutely terrifying.

Why terrifying?

We talk on top of each other in this play . . . which is incredibly difficult, knowing just when to come in near the end of someone's line, but not too soon that you talk over stuff the audience needs to hear, but not too late that things slow down. It's this rhythm and it's . . . it's . . . .

Sounds like being part of an orchestra. Sometimes you're playing harmony to someone else's melody.

Exactly. That's good. I like that. Your brain has to work in a very different way than what it does when you're playing tennis. I like tennis -- "acting tennis," that is -- where it's all about listening to what a character says, then reacting, delivering a line back. In this, we do that, while waiting to hear specific words when you're supposed to jump in.

Must take lots of rehearsing.

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Yeah. But you can't let it sound too rehearsed. It has to sound natural. It's weird how your brain is doing all that at the same time. You're trying to be in the moment, make new choices each day, to keep it real, but still get the lines delivered at the right time . . . because if you're late, it messes everything up.

Which sister are you?

Amy, the middle sister, who's planning her wedding. All three sisters lost their mother when they were young. Amy grew up sad, lonely, in need of love . . . and so that's why . . . (she pauses, chuckles) . . . she's a bit of a bridezilla.

Do you get to hang out much with the other two actresses playing your sisters?

It feels like summer camp. We spent the last two months, every single day, together. Except Mondays. But we text on Mondays. I didn't get to go to college, so this is like my fantasy of that. But as far as hanging out, we haven't had much time outside rehearsals. I come home very fast to my son each night.

How old is Bear now?

He's 4 . . . and sooooo delicious.

It's nice you have him with you.

I'd never go anywhere without him. He loves coming to the theater, and pretending to be our stage manager. Each night, he tags along with the actual stage manager as she makes sure the props and things are in place. They made him a clipboard, with little things he has to check off, so he's really into it.

You lead quite a healthy life. You're vegan, you speak out against animal cruelty, you have solar panels on your house . . .

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There is so much going on . . . and it can sometimes feel overwhelming. But there's a lot we can do, and it doesn't take a lot of time.

Is there something you still struggle with? Some dirty little secret like . . . do you sometimes wolf down a Twinkie?

I have dirty secrets, but they're secrets. I'm a human being. My whole creed is that you do the best you can. Sometimes you have a hiccup. If I'm perfect 99.9 percent of the time, that's great but I don't sweat that .1 percent -- in fact I want that there to remind myself -- yes, it's OK. I'm a little tough on myself, and in the beginning, I tried to be perfect and it just became . . . impossible. I've committed to making healthier choices for my health, the environment, for animals, and people around me . . . and if I fall off for a second, so what? Then I'll get back on.