Theory on why and how Krillin grew hair during the time skip:

"Krillin! You've violated our sacred laws of monkhood!" A voice echoed through the house of Kame. Krillin awoke to find a bald, old monk staring straight into his face.

"Augh! What gives! Is that you, Master Roshi? Oh crap, it's my other Monk Master! I haven't seen you in years!" Krillin jumped out with a start.

"Krillin! We won't allow you to pursue 18 any longer! You belong with us, in the temple, praying, meditating, and training forever! Your baldness proves you are still a monk and must abide by our rules! Till then, we'll keep on haunting you… haunting you.. haunting .. .. .." The bald, old monk said in his eerie, creepy voice. Then slowly, he starts to fade away.

This time, Krillin really wakes up from his nightmare in cold sweat. He then quickly finds Master Roshi for advice.

"Master Roshi! I don't want to be a monk anymore! How do I do that?" Krillin yells.

"Grow some hair, then! Monks don't have hair!" Master Roshi replied, his eyes still glued onto the television.

"Okay, Master Roshi! I need to grow hair, quick!" Krillin yells again.

Master Roshi looks at Krillin in puzzlement, then points to his own, bald head. "Do I look like I can help you with your hair troubles?" Master Roshi chortled. "Go buy some hair tonic or something! And stop bothering me, I'm busy!" Master Roshi then starts to drool. "Man, these girls on TV sure are flexible!"

"Right. Hair tonic. I'm off to buy hair tonic then!" Krillin then takes off to the nearest super mart.

*A few weeks later..

"WHY WON'T MY HAIR GROW! I've tried all sorts of expensive hair treatment with not the slightest result! Maybe I should just accept my fate, be haunted by the monks forever, and not pursue 18 any longer even though she's so cute.." Krillin cries out in frustration.

"I heard my number" A familiar voice said from behind. Krillin spins around and finds 18 staring at him with arms folded.

"E-Eighteen! What a coincidence!" Krillin stammers. 18 grabs his arm and pulls him away.

"You wanted to go on a date? Fine, let's go. I'm bored anyway." 18 smiles an evil grin and proceeds lead on their date.

"Buy me some clothes," 18 instructed. Going into the clothing store, they find Master Roshi peeking in the women's section. 18 ignores him and points to a ridiculously expensive apparel. "I like that one. Get it for me."

"Wh-what? That's too expensive, I don't have that kind of money!" Krillin then turns to look at a dangerously fuming expression on 18's face. "I mean, I don't have that money yet. Wait here." Krillin corrects his statement and makes his way towards Master Roshi.

"Psst. Master Roshi. I need some money"

"Go away, Krillin. I'm busy"

"Lend me some money or I'll tell Bulma what you did with her undergarments."

Master Roshi freezes momentarily and turns his attention to Krillin.

"You wouldn't.."

"Would you like to risk it? Especially since Bulma's with Vegeta now" Krillin whispers to Master Roshi.

"Fine. Take my whole wallet then. Miserable, ungrateful student of mine #$!.."

Master Roshi then hands Krillin his wallet, who then proceeds on to buy the ridiculously expensive clothes.

"What did you just do there?" 18 asks Krillin after he hands her the gift. "Oh, nothing. It's called blackmailing." Krillin responds.

"Blackmailing? What an interesting concept. I think I'll try that out on someone next time." 18 then glances around and notices posters of Mr Satan everywhere. "Blackmailing the richest liar on Earth would be interesting. You're not bad. I like you. Just wish you had more hair though." 18 then proceeds to give Krillin a small kiss on the cheek and Krillin blushes.

"YEAAA I am definitely gonna grow hair on this head for sure!" Krillin shouts out in his mind.

Cue Eye of the Tiger music while Krillin frivolously searches for a way to grow hair in the following months. He finally succeeds and now has a full head of hair.

*Epilogue:

"Krillin.. Krillin..!" The figure of the bald, old monk appears in Krillin's nightmares once again. "The rules of monk hood clearly states that.."

"Go away! I have HAIR now!" Krillin rudely interrupts, and the figure disappears. Krillin then never has those nightmares again.