Rhubarb's first instinct was to run. And that's what he did. He ran towards the nearest window and opened it. The changeling was halfway out the window too when Merry bit onto his tail and yanked him back inside. She closed the window and glared at him. "You won't solve anything by running."
"I did once!"
"That was different!"
"...Rhubarb?" Mr. Cake asked slowly.
Rhubarb cringed and closed his eyes and then peeked back behind himself. "...Yes? Please, please, please don't freak out, just let me explain." He began hyperventilating. "Oh dear, this wasn't how I wanted you to find out. Is the room getting hot or is it just me?" Sweat fell down his face profusely.
Merry shoved him aside. "Mr. and Mrs. Cake, Rhubarb's a changeling."
"Yeah, I think we got that." Mrs. Cake said, still blinking in confusion.
"See, he's...he's much different than the other changelings. He left them months ago. And--"
"I got this, Merry..." he sighed heavily. "Listen to me, Mr. and Mrs. Cake. I know I lied to you..." He picked up a confused Pumpkin and Pound Cake and gave the babies back to them. "And I know you don't have to trust me, but...please. Can you just let me explain?"
Mr. and Mrs. Cake shared a look, and then Mr. Cake nodded. They then walked to his couch and sat down, looking to him for answers. Their eyes were large and shocked, but they were willing to listen. Rhubarb closed the door and turned to them. With another breath, he changed himself into his true form. He heard the couple gasp and Pound and Pumpkin giggle.
"I was never from Fillydelphia. I came from the dark recesses of the changelings' lair...for all I know, though, the queen could be residing in a castle right now. She always mentioned to the hive how she wanted a castle." He shook his head, scoffing. "That's beside the point. Anyways, I...never saw eye to eye with the others. As a kid I tried baking and loved it, and when the others found out, they just about lost it." He shuddered with memories. "So when the queen announced her plan for Canterlot, I fled, masked as a unicorn, and finally found a job and a very special somepony." He looked to his girlfriend, who nodded proudly. "I didn't tell anypony because I was worried my perfect little world of peace would shatter. Merry May found out only weeks ago."
After a couple minutes of extremely awkward silence, Mrs. Cake sadly frowned. "Oh, dear, all this time? I would ask why you said nothing, but I think I know why."
"I know." Rhubarb rubbed his head. "And please, please don't fire me. This job and this life in Ponyville means everything to me. Please--"
"Rhubarb, why in Equestria would we fire you?" Mr. Cake asked. Rhubarb's eyes burst open, making his girlfriend giggle. He had what could be called a surprised deer face. "I, for one, don't care," Mr. Cake continued, "you make good food fast, and the bakery has benefited from your help. In spite of the fact you lied about where you came from, we understand why you did it."
"Oh my Celestia," Rhubarb said, practically dropping to the ground in relief, "Oh, my Celestia...I was so scared." Mrs. Cake then got up, approached, helped him up, and hugged him. Although a little surprised by the hug, he returned the hug warmly.
Outside the front door, Pinkie Pie was waiting impatiently for Mr. and Mrs. Cake to finish up and get the fillies. She was waiting below the apartment building, when finally she went up the stairs to find out what was going on. The earth pony heard soft murmurs inside she couldn't make out, so she planted her flank down and waited.
Finally, she lost her patience and opened the loose door to find Mrs. Cake hugging Rhubarb as a changeling. Rhubarb pulled back from Mrs. Cake in more shock. "I...Pinkie Pie!"
"Now, Pinkie, listen--" Mr. Cake was cut off by a excited squeal and the door being closed.
"Finally, somepony comes out of the changeling closet! About time, Rhubarb!" Pinkie exclaimed, not looking shocked at all. Rhubarb's eye twitched.
"You knew?" he asked. Pinkie nodded.
"Of course I knew! Now, I may be a party girl, a baker, and...a party girl, but I'm not stupid. I saw all the signs. When I saw you at the wedding, I noticed your magic had the very same tint of green that a changeling's magic had." she said, pulling a detective hat out of his chimney and puffing into a pipe she pulled out of her hair that exuded bubbles.
"I hardly see how that's proo-"
Pinkie ignored Scales. "So, to make sure it wasn't a changeling that had taken over your spot or anything, I tackle hugged you. You reacted as only Rhubarb would react. Not to mention you were all sad before and after the wedding. When I noticed you walking off at the end of the party, I asked Princess Luna to talk to you. I knew you wouldn't say a darn thing to me if I asked you what was wrong." Pinkie puffed into the pipe, pushing more bubbles out of the end of it.
"Really, Pinkie, I--" Rhubarb had not a chance to speak.
"She then told me how you were feeling a bit guilty. But she wouldn't say over what. The princess was respecting your privacy. Perhaps if you heard about the wedding from the changelings months ago before you met us, then you would feel guilty for not saying anything. And I know you. You work yourself to the bone so you don't think when you're upset." Proudly, the pink pony grinned. "Not to mention when you came here for the first time, you had nowhere to sleep. Fluttershy distinctly mentioned how a strange sparrow flew into her house every night. Then it stopped as soon as you got an apartment."
"That doesn't--"
"So right then at the party when I tackled you I was positive you were a changeling! Ta-da!" Pinkie declared. Everypony stared at her silently, not exactly sure how to react. Pinkie clapped her hooves together. "And now you're coming out to us! Woo-hoo!" She tackle-hugged Rhubarb again.
The changeling coughed and when she let go, he got up. "And you knew all this time and said nothing?"
"Uh, duh!" Pinkie rolled her eyes. "It's your secret. I'm not gonna force a friend to talk about something they're not comfortable about. And to tell anyone would betray the trust you put into me. And betraying a friend's trust is the fastest way to lose a friend! Forever!"
Rhubarb said absolutely nothing as everypony else laughed. Merry May stopped all of a sudden and began examining her boyfriend's legs. Rhubarb gave her a strange look. "May, what are you doing?"
"Your legs! You hardly have any holes at all now!"
It was true. An examination proved that there were almost no holes, a maximum of one per leg at this point. And those holes were getting smaller. Merry whimpered. "Rhubarb, I'm worried about you! What if something's wrong?"
"I'm sure nothing's wrong!" Scales exclaimed, throwing a hoof into the air. "I feel fine, and I can change just fine too."
"But honey, I'm worrying about you. We need to get you examined by a doctor."
"Merry, I don't know if they'd know what to do any--"
"I don't care. Listen...Pinkie and the Cakes know and they still love you. I know and I still love you," Merry said frantically, "listen, Twilight Sparkle and her friends are the bearers of the Elements of Harmony. Twilight herself is the personal student of Princess Celestia. Let's tell them and ask them to take us to the princesses for help. Maybe they have a doctor or something that can look at you."
"She's right, you know," Pinkie said, "I can guarantee the others will love you just as much as we do. I don't know how holey you used to be, but your lady is worried and I won't stand for it!" she shouted.
"And we can't afford to have a baker sick." Mr. Cake said. The babies nodded in agreement, though they didn't understand a word that was said. Scales was overwhelmed.
"I...you're really all that worried? I'm fine, I'm sure."
"Please. For me?" Merry said, making large puppy eyes. Scales was quiet and gave in.
"Fine," he said in resignation, "But I'm not at all happy about this...hm..." he thought for a minute. "Alright, here's the plan..." he began as everyone huddled up to listen.