Derek activated his monster transformation first.
he covered his eyes with his hands, and then, uncovered them, or more rather, the one eye.
He had a cyclops eye!
Then, David pulled off his sandals, socks, shirt, and jeans, stripping to just his underwear.
his Neck extended longer, pushing his head onto a stalk.
his arms and legs became more muscular, his feet became bigger, and webbed, as did his hands.
Spines grew on his back. they were short and stumpy, like on David's monster form, but they were blue instead of brown.
Finally, Derek's skin turned a lavender colour, from head to toe. his hair remained the same colour, though.
David was amazed. "Wow!" he said. "You look almost like a giraffe!"
"I know." Monster Derek said. "I always liked giraffes since I was a kid. I often imagined what it'd be like to have a long neck like they do."
David watched as Derek's clothes [minus his underwear] disappeared.
"How come you're still in your underwear?" David asked Derek.
"Well," Derek said, "I set my tf to keep my underwear. It's the one exception to the 'MonsterMen don't wear clothes' rule."
"Yep." Dennis said. "MonsterMen aren't to wear any clothes, unless they decide to keep their underpants on them. That's one of the rules."
"The other rule is 'Don't let anyone outside the MonsterMen club see your monster form." George added.
"Thankfully," Roger said, "as I said earlier, We set the tfs so that only we can see ourselves tfin'."
"Well, thanks." David said, "so, who's gonna tf next?"