Don't wear them

He thinks about it, but decides against it. Panties and a bra would be way too humiliating. Even if his body was female, he still had his masculinity to think about. And if no one was going to see his underwear, there was no reason towear panties.

"I'll... just stick with the outerwear, thanks," he says. "Could you turn around while I change?"

Sam nods and turns, and Tripp starts changing. He closes his eyes when he drops his pants. The sight of his new... organ wasn't something he enjoyed. It was hard to feel like a man when his manhood was gone.

He finishes changing and taps Sam on the shoulder to let her know he's done. "W-well? What do you think?"

Sam turns around and grins, trying her best not to giggle at the sight of her once-boy friend wearing girl clothes - even if he was a girl now.

"Aw, I've always wanted a gal-pal! You look so cute! Mmm, you have quite a nice figure, too. Curvy in all the right places."

Tripp blushes and pulls at the fabric of the sweatpants. "It's a little tight in the rear, isn't it? The chest too..."

"Oh Dawn, honey... that's where you want it to be tight when you're a girl. You have so much to learn."

Tripp groans. "I don't want to learn how to be a girl!"

Sam ignores him and sighs, looking wistfully into the distance. "Ah, it's a shame you didn't try on the panties. I would love to turn you into a girl permanently and do all kinds of stuff with you that I can't do with boy-Tripp... Hey maybe we should ask Al and see if that's an option."

"Sam!"

Sam giggles. "What? I can't help it, you're an easy target!" She leans in, putting both hands on Tripp's hips, and whispers into his ear, "I think it was really brave to go without panties. Way sluttier. I do that too, sometimes. You know... When I'm wet..."

Tripp turns tomato red and reels backwards.

Sam bursts out laughing. "See! Oh my gosh, you're too easy, wittle Twipp! Or should I say, wittle Dawn!"

Tripp fumes. But at least it was over. He successfully put on clothes that fit without wearing panties.