Toddler Who: Team Tail

  "Sandshoes! Sandshoes!"
  Two spiky-haired boys would've caught the dark-topped kid in swimming trunks with bowtie pattern if it was not for a blond little guy who lost no time in jumping right onto the large running shoe built out of sand.
  "No more sandshoes!" John Simm yelped, happily demolishing the remains of Matt's work. "What? I saved Mattie from ya two!"
  David and Johnny immediately turned away to chase him, while Matt, having forgotten about his spoilt 'sandshoe', ran to watch Colin and Chris who were having a mock football match. Some of the adults, who were located at the higher point of the beach to watch out for all of them, suspected that Peri and Rose, Colin's and Chris's sitters correspondingly, would soon have to take part in this. Out of all gang only Billy was behaving, sitting with a storybook farther from everyone - he was almost the only kid here who had mastered reading yet.
  While the children were having fun in their own ways, little Patrick decided to take a treasure quest. His sitter Jamie had a habit of stuffing his pockets - if he wore things with pockets, for he preferred kilts, much to most people's dismay - and bags with everything he could find: wire bits, ropes, threads, nuts, screws - everything, for he earned a living not only babysitting Patrick, but also mending musical instruments, and this all could come in handy. And after having nicked Treasure Island from his parents' library, Patrick was sure that every beach could hold a treasure, it was important to search only.
  Part one worked finely: Patrick managed to sneak away from the group, and for the first time he mentally said thanks to Mels, who had a fight with Simmy for having ruined his sandcastle in revenge for Matt's. This was a nice distraction. But part two threatened to finish before it started: Patrick was running along the seashore until it was quiet around him. The group chose this place because it was secluded and no one was there to spoil the fun... but now it didn't seem such a good idea. Patrick wanted to get away for a moment, but then he caught himself on a thought that it would've been unforgivable to lose such a chance. No one was around - only himself, sea, sand and rocks.
  "I'm not doing anything wrong, only looking," Patrick said aloud, gazing at the rocks times higher than highest adults. "Nothing wrong..."
  At first it seemed lucky: he found a handful of colorful pebbles and green glass pieces smoothed by the sea, which he quickly hid into his shorts' pockets. After some more searching Patrick saw something shiny right under the closest rock. What could it be? He set off to digging, but before he could've seen what it was, the ground under him begin shaking, and he suddenly found himself falling down.
  "Help!" Patrick shrieked - now it was more like sliding down a slimy hill. Luckily the flight wasn't long: the leaning surface was gone, the boy flew a couple of meters and landed with a splash. When the dizziness and fright was gone, he realized that he was sitting in some kind of an underground pond or a well.
  "Where did you come from?"
  When Patrick's eyes got used to darkness, he realized that there was someone else here. He couldn't see clearly who it was, but his voice sounded benign, and this was something.
  "I think from... up there," Patrick replied, looking up in trials to see where the unreachable entrance was.
  "Oh my word, I just knew that someone nosy would get here."
  "I not nosy," Patrick mumbled. "I was searchin' for a treasure... Will you get me out of here? Please?"
  "I suppose I could. Can you swim?"
  "N-no..."
  "That's bad news. And can you hold?"
  "Of course," Patrick nodded.
  "That's good news. Come here and hold..."
  Patrick obeyed, having clutched two folds of fabric over the stranger's shoulders.
  "Now hold tightly and don't let go at any price, if you don't want to drown."
  At the first moment Patrick almost let go because the stranger darted forwards too briskly. Wow, no one could swim so fast! - he thought. And 'riding' like this through darkness and water appeared to be creepy, but thrilling as well. Anyway, when there was a hint of daylight, Patrick's heart was ready to rip out of his chest.
  They ended up in a cave half-filled with water. It was a beautiful place and also perfect for hiding treasures, but Patrick wasn't thinking about this anymore.
  "Well, I got you out, child," the stranger said. Now it was possible to see what he was like. He had a shock of thick jet-black hair and pale blue eyes, and signs of age as well - eyebags and skin folds which hinted about being able to smile. He was wearing some kind of a white tee with elbow-length sleeves, and the rest wasn't seen because he was leaning on a rock on which Patrick was sitting. "Who-hoa, you do remind me of someone. What's your name?"
  "Patrick," the boy replied, having caught his breath.
  "And I'm the Doctor," the stranger said.
  "Where are we?"
  "A small island not far from the shore. It was the only way from the well into which you fell. Guess there was someone who didn't care about kids' safety when hiding it."
  "And what were you doing there?"
  "Searching," the Doctor said. "Just like you. Searching for a particularly nasty beast."
  "Beast? Are there beasts here?"
  "Don't worry, I've already taken care of it."
  "Doctor! Doctor!"
  "Jamie!"
  The latter was exclaimed by both of them upon the sound of the third voice. A long pause followed, after which Patrick jumped up and dashed in the direction of the familiar voice.
  "No, wait!" the Doctor yelped, but it was too late. Patrick ran out of the cave and froze with his mouth open.
  It was no doubt that the youngster sitting on the shore was Jamie McCrimmon - Patrick would've never confused this appearance with anybody else's. But there was also something that made him doubt his vision. Jamie's top half was perfectly his, but waist down was a completely different story. For some reason his legs were replaced by a fish-like tail covered in brownish red scales, and it didn't seem fake at all. Why would Jamie want to prank him?
  "Doctor? What, you overdosed with that appearance thing?" odd Jamie asked, and Patrick found no other way than to run back. He's better not done it, because it came clear that this 'Doctor' had this kind of oddity as well, though of different color. In his case it was electric blue.
  "Unbelievable!" the Doctor said, pulling himself onto the sand. Poor Patrick didn't know what to do - in some tales, mermaids were kind to people, but in others they were wicked beings with a taste for kidnapping. "Totally unbelievable!"
  "What is?" Patrick muttered, wildly looking around.
  "That is, my dear boy, that you're me in this world!" the Doctor exclaimed. "I knew that we landed close to the location of our possible doubles, but I didn't see that coming!" He went on, counting on his fingers (thank goodness without any webbing between them): "One: you share your appearance with me. Two: you recognized Jamie. Three: Jamie recognized you. Four: you... you... No matter!" he shouted and laughed. "Now we only have to wait, have to wait, to wait... Don't worry, Patrick, it's a temporal state."
  "Hai?"
  "I'm not a merman, just for a time," the Doctor explained. "Had to enter a vaccine for underwater breathing to accomplish this mission, and this dose would have to wear off after 24 hours, but the time's not over yet, so we have to wait. And those are all side-effects. You know, merpeople breathe with their skin and all."
  "So your Jamie is not... my Jamie?" Patrick pointed out, his fear slowly leaving.
  "He's not. Just the same face," the Doctor explained.
  "And... will you get me back?" Patrick asked. "I don't want my Jamie to shout at me."
  "Does he?" the Doctor wondered, lazily splashing his fins over the water.
  "Not often. When I deserve it," Patrick confessed.
  "Heard that, Doctor?" sounded from the side of the shore. The Doctor mockingly shook his fist at the voice source:
  "Wait until I get my legs back!"
  "This is going to happen in three hours fifty-two minutes." Another person joined the conversation. This time it was a girl with chin-length dark hair and fragile stature, and with a tail as well - in her case it was metal grey, as well as the sleeveless tee covering her top part. "So make sure you won't forget. I'm not reminding you."
  "Zoe, meet Patrick. He's me here." The Doctor was speaking as if talking about something ordinary, like buying soap.

  Jamie was beginning to get desperate when a little blur of dark hair and shorts jumped into his arms and clang to him.
  "Patrick! Where have you been? Everybody has been searching for you!" Jamie exclaimed.
  "Jamie I was searching for a treasure and fell into a well and met a man who was me but in another world he was called the Doctor and there was also another you and a girl named Zoe and they all had tails like mermaids and they brought me here I'm sorry!"
  "Patrick, couldn't you think of something more persuasive?" Mrs. Williams asked.
  "But it's true, Mrs. Williams!" Patrick exclaimed. "True-true!"
  "The only truth here is that you've been gone all day and now think of things not to be punished," Tegan. Petey's sitter, mentioned. Patrick pouted, but a moment later there was a very familiar splash and chuckle. It was Jamie chuckling, but he didn't say a word or even moved his mouth. So who could it be?
  Patrick wriggled out of Jamie's grasp, ran over to the shore and gathered some large scales of brownish red, electric blue and metal grey colors - each was as large as a ring shaped out of forefinger and thumb:
  "Look, that's theirs!"