Mark yanked hard at the diaper again, and it finally pulled down a few inches. He felt really strange, and something told him that taking the diaper off might be a bad idea. But he didn;t want to get stuck in it, and he yanked hard again.
This time, the tape popped apart on the sides and the diaper fell off. Along with all of Mark's other clothes. Mike and Sei were pulling at their own diapers, and he realized they looked younger - maybe 14 now, and shrinking to 13. But they stared at him and stopped trying to get their diapers off. Sei gasped and said in a higher voice - "Put your diaper back on, quick!"
Mark looked down and saw that fur was spreading over his body. He fumbled for the diaper as his penis changed to the sheathed nub of a puppy, and he fell forward onto short, stubby legs. It was getting hard to think, and his hands and feet were now large paws. He yipped at his friends, who were now 8 years old.
Mike stared in amazement. "You're a Great Dane puppy!" And both of the little boys grinned as they shrank to age 7 in their diapers. A puppy to play with!