I'm not the person you replied to. But in case they never get back to you, Dbz abridged did a lot of stuff to flesh out characters and plot. They kept a vlog going when they were recording and basically they got really really bored with the bit 1/3 into recording the series and decided to just start spicing up the writing in a lot of places to keep themselves entertained.

For Krillin they wrote all the various L's the show hands him as eventually contributing to a down-to-earth, unassuming, and resilient personality by the time he meets the androids. 18 on the other hand makes various jokes about having nebulous and inscrutable preferences in body type. She values in-group loyalty over other forms of morality so when they meet Cell and he immediately understands the Cell situation and begins working to save the other androids there's at least a bit of a throughline for why their attraction was plausible. Though TeamFourStar did still play 18's immediate magnetism to him for jokes.

DBZA, when Krillin decides not to blow up 18 because she's pretty and he's in love, and to stand up to Cell so she can escape:

If we make it through this, I am going to rock his four-foot world.

• 18, true love.she also calls him "the cute one" a minute before that.

Oh yeah, also after 18 kisses him, he brags to Yamcha, who dropped out early after getting Yamcha'd by 19 and 20: (Krillin) "and I got kissed by the cute one!" (Yamcha) "... the clown?" (Krillin) "No no no, there's a girl now"