Going back in time a little bit...
"Do you see this, too, Raditz? It's the end!" Goku asked his brother, not believing his eyes.
"Finally! I thought we'd never get here!" Raditz agreed. Excited, they raced to the end. Goku accidentally jumped partially off of it, but Raditz managed to catch him before he fell through the clouds.
"Is this some kind of bad joke? There's nothing here!" Goku complained.
"We go all this way for an endless stretch of nothing!? Are you kidding me?" Raditz yelled.
"Wait, look there! It's some sort of planet."
"Fairly small." Raditz noted.
"King Kai must live there! Come on! Let's check it out!" Goku and Raditz flew up to look at the planet, but they were soon drawn into its gravity well.
"What gives! The gravity's so intense! You have to be super strong just to stand up in here!" Since Raditz wasn't wearing weighted training clothes, he had an easier time that Goku of standing up, but it was clearly no picnic for him, either.
"This gravity... It reminds me of the gravity on Planet Vegeta." Raditz reminisced fondly.
"What?" Goku asked.
"The planet that we were born on, Kakarot. Its gravity was just as bad as this. I forgot all about that, it's been so long."
"Either way, this is insane. You have to be super strong just to stand up here."
"At least we made it." His brother told Goku.
"There's a house. It's got to be King Kai's place." Goku said. Since he was stronger than he had been in the anime, he wasn't struggling too much with getting the words out, but he still struggled to stay on two feet.
"Wait a second. I thought I smelled food. Let's get some fruit off of that tree." Goku decided. The two tried to get up the tree, but they struggled with it. Finally, a certain monkey climbed right up their shoulders and into the tree.
"Why you! You're not light, you know!" Raditz complained as the monkey stepped on his shoulders, nearly causing him to fall onto his butt.
"Are you King Kai?" Goku asked the monkey.
"Kakarot, that's a monkey."
"Who says King Kai can't be a monkey?"
The monkey looked on from the treetop as the two siblings bickered.
"Either way, we're really hungry. King Kai, can you throw a couple apples down for us?" Goku asked the monkey.
"That isn't King Kai, Kakarot. It's a monkey." Raditz declared. Immediately, an apple landed squarely on his head, knocking him unconscious.
"Raditz!" Seeing that his brother almost immediately stirred, Goku called up to the tree again.
"King Kai, can you throw one down to me now? Please don't drop it on my head, by the way." The monkey obliged. Goku barely managed to catch the incredibly heavy fruit.
"Stupid monkey." Raditz complained, rubbing his head and picking up the fruit that had landed on his head. Despite his complaint, he still bit into it.
"Sorry, King Kai. We were just hungry. We came here a long way to learn the secrets of martial arts from you, and we're ready now. Please teach us." Goku bowed respectfully to the monkey.
"Kakarot, that's a monkey."
"Ooh ooh, ooh hoo ooh, ooh ooh ooh." The monkey walked off, holding its hands above its head and doing a little dance as it chattered.
"I think he wants us to follow him?" Goku decided, confused.
"Kakarot. That. Is. A. Monkey." Raditz repeated.
"If you keep disrespecting King Kai like that, he may decide not to teach you, Raditz." Goku countered with. Goku started following the monkey, mimicking its dance and chattering. He quickly realized how difficult a workout that was in this strong gravity.
"Slow down, King Kai! This is a lot harder than it looks! Ooh ooh! Ooh ooh!"
"Kakarot."
"Ooh! ooh!"
"Kakarot."
"Ooh! Ooh!"
"KAKAROT!"
"I thought I'd seen it all."
"uhh... who are you?" Goku asked. Was it possible that the monkey wasn't King Kai?
"I am who I am. Guess who? Guess! It rhymes with pie." the blue man paused for a moment, "Got it? I'm King Kai!" Raditz put his hand over his face in exasperation.
"Then who is he?" Goku pointed at the monkey.
"A MONKEY!" Raditz yelled at his brother.
"He's my favorite monkey, Bubbles."
Goku started laughing. "I see, I thought he was a little strange."
"Says the guy who thought that the martial arts master was a monkey." Raditz muttered.
"Did you just call my friend bubbles strange? Like you're not."
"Huh?" Goku's eyes widened. A critical hit!
"Now don't take it personally, I'm only teasing you, son. Even Kais like to kid around." King Kai told Goku.
"Y-yeah... me too." Goku told him.
"Kakarot... we're not here to kid around." Raditz scolded him.
"If you're not, then why are you here?" King Kai asked.
"Martial arts training, sir." Goku told him, "I really need to get stronger."
"Him, too?" King Kai nodded at Raditz.
"Yes, sir." Raditz nodded.
"Hmm..." King Kai paused for a moment, thinking, "Fine. But first, you each will need to tell a joke. Make me laugh, and you're in. I won't train anyone who doesn't have a sense of humor." He told them. Goku and Raditz looked at him dumbly.
"Nope." Another voice carried itself through the area, confusing all three of them. None of them had sensed another person.
"Who are you?" King Kai instantly turned to face the person, a young girl who was leaning against his house, "It's rude to sneak up on people, you know."
"It's you!" Raditz instantly recognized her. She hadn't given him her name at the time, but it was the girl who had given him his second chance at life.
"Ohh, yeah. Wasn't she watching our battle a while back?" Goku thought aloud, recognizing her face.
"I'm Shay. My Mistress sent me to ensure that you two actually got here. Just train them, blue guy." Shay decided. She hadn't seen her Mistress in person in over a month, and she was getting incredibly annoyed. She wasn't in the mood for jokes.
"And why should I? I refuse to train someone without a sense of humor!" King Kai argued stubbornly. In response, Shay raised her hand and collected enough power above it to vaporize his whole planet and then about half of Snake Way. Seeing it made King Kai's face pale. "Absolutely! As you wish, ma'am!" King Kai turned towards the two Saiyans and dropped into a fighting stance.
"Come at me you two! Hurry up, I don't have all day."
"Wait... What just happened? Is she really that much stronger than you?" Goku wondered aloud.
"Yup. Don't concern yourselves with me, though, monkey boys. I have my own agenda, so I'll just be right over here watching."
"What do you mean? Why did you help us?" Raditz asked Shay.
"I follow my Mistress's orders." Except for the part about releasing Raditz from hell. That one had been totally on her.
"So you won't train us instead of King Kai?" Goku wondered. After hearing how much stronger than him she was, Goku was itching to learn from her, but Shay shook her head.
"Mistress doesn't want that. Just learn from the blueberry."
"Hey! Show some respect! I'm still a Kai!"
Ignoring him, Shay sent a telepathic message to her Mistress while Goku, Raditz, and the Kai started their training. Unlike in the anime, they actually had a small training bout before King Kai told them to chase his monkey. Naturally, King Kai smoked them both.
Mistress, they finally arrived. I miss you. Shay sent.
They...? Whatever. Good job, Shay. Hang in there a little while, I'm still watching over Gohan. Her mistress answered back.
Understood, Mistress. I'll just stay here, then... The sadness in Shay's message was palpable. She didn't like distressing her Mistress, but she really missed the girl.
Hey, perk up. Eight months sounds long, but it's not really. We can chat all the time. What are they doing now? Her Mistress asked.
Having a training match. It's soo boring! When you've got your energy pumped down, it's adorable, but when they do it, it's so sad. Shay answered back. Her Mistress simply let out a long sigh.
This is gonna be a long eight months...