Of course, you knew exactly what your friends were saying, but you knew they'd want to see what each other wanted and see the changes as they happened.
"Karen, Ashley, please," you said. "One at a time. Karen?"
"So you said we could have multiple forms if we wanted?"
"Of course. Anything for the best friends an omnipotent goddess could want--well, except omnipotence yourselves. There are a few limits on my power--not many--and that's one."
"Could you maybe create a simulacrum of me? Just so we can all see the changes."
"Sure," and a naked Karen popped into existence nearby.
"Okay, well, I think you both know that I've dreamed of being a huge giantess, so I want to be able to make myself grow."
"How big?" you asked.
"Ten miles? Is that too big?"
"It's a good starting point. All right, here's you at ten miles. You'll also be able to go anywhere in between." A city stretched out beneath the simulacrum. Karen's feet covered some of it and you could see the earliest signs of sexual arousal in your friend.
"I also want to be able to enlarge my breasts and butt so that I can crush things with them." In turn you enlarged the breasts and butt of the simulacrum until Karen indicated that she was satisfied with their maximum size.
"Those are your maximums, but they'll scale with you proportionally."
"And I'd like my hair to be able to reach the ground if I want, so I can swing it into buildings. Oh, and I want to be able to lengthen my tongue and lick up people from the ground." You applied the changes.
"And what do you want as your normal form? This one at least has to be reasonably sized, but you can still have big proportions if you want."
"Hm," said Karen. "Maybe 7'6", breasts out to here"--she gestured a fair distance from her chest--"and a butt to match, hair brushing its top?"
The simulacrum changed to show this form for Karen, and she smiled in satisfaction. You turned to Ashley and prompted her to begin, creating a simulacrum of her.
"Well, I've got this multiple limbs fetish, and so I was hoping it wasn't too weird for you..."
"Nah. To be honest I've had lots of fun giving myself an extra pair of arms sometimes, really helps out in certain situations."
"Okay, so I want to be able to give myself extra arms, maybe ten pairs"--the simulacrum changed to show the extras--"and more breasts, enough for the arms, and more legs, maybe eight, four in front, four in back? Oh, and two extra heads. I know a lot of people wouldn't like this but I just always have."
The simulacrum showed Ashley with all the changes she'd wanted. "Okay," you said, "like Karen, you can go anywhere in between. Also, both of you will get clothing to suit when you change. What body do you want for your usual form, Ashley?"
"Well, I have this other thing..." You knew, of course, where she was going, but let her continue. "I just really like seeing people who are completely identical, at least to my eye. I was kinda hoping you two would be willing to have us look like identical triplets normally, except I guess for the clothes, make-up, hairdo, jewelry... But our bodies should be the same."
You were indifferent on the matter--it's not like anything you did was irreversible--but looked at Karen. "What the hell," she said. "It'll be fun."
The three of you morphed into tall, busty women. You decided that the three of you should have purple hair, something more to set you apart from everyone else. Of course, to everyone else, it was completely normal.
"Also, Ashley, when Karen makes herself into a giantess, you're completely immune from anything she does."
"So I'm immortal?"
"No, not until I'm sure you can handle immortality. And if you start doing really foolish things like throwing yourself off cliffs with no safety precautions... well, sorry, but I'm not making promises to bring you back to life in that case. Doesn't mean I won't, though, but don't count on it. And Karen, you can rampage as much as you want, but I'm probably not going to let it stick. And they certainly won't remember it, at least not after I fix it. Still, I might let it stay for a while. And I promise you'll remember it."
You changed reality so that nobody would question how three nerd girls were instantaneously replaced by what appeared to be insanely sexy identical triplets--for now you all even had the same clothing, accessories and hairdos--and unfroze time.