All this starts off with Jack thrown in Johnny’s timeline/world of course.
At first, Johnny would honestly think that Jack is just a pretty boy. (He’ll probably hang out with him at first because Jack reminds him of Squint Ringo, his favorite actor) Then maybe confused as to why he isn’t as annoyed with him as he is with his other companions. When he finds out that Jack is very popular with the ladies, he’ll go into investigation as to why and finds that Jack is actually really cool. But THEN when he learns that Jack has super talented fighting skills??? Jack is now someone Johnny strives to be (but he’ll never admit it to himself because Johnny’s the only hunk in Aron city right??)
Linking back to where Johnny’s a huge fanboy for Squint Ringo.
Can you imagine how he’ll feel about Jack, when Jack is like 10x times more hotter, skilled, brave and overall FUCKIN GREAT HUSBANDO MATERIAL??? They would be really good friends at that point but I bet what tips him over into crush zone is that Jack (in all his GLORY MIND YOU) actually likes his weird antics and thinks he’s a very interesting character. (Johnny will take any compliments, but coming from Jack? That’s a lot of taken in) I think the fact they both are “out of the norm” is what makes them mesh pretty well too.
But in canon, Johnny actually knows that he has problems with intimacy and he pushes people away because of it. So Johnny would have a extremely hard time admitting that he cares about Jack. Johnny also has issues with his self-esteem, so internally he’ll be too much of a coward to ask Jack for a date in fear of rejection. He genuinely likes being around Jack, why would he risk losing that?
But of course in Jack’s perspective, when he meets Johnny, his first thought would be that Johnny would maybe friendly enough to show him the way of his world he’s temporarily stuck in. He’ll see Johnny’s antic very amusing and his regards to women as a very strange custom (noting himself to not follow it because of the painful repercussions of it). He’ll have a lot of weird adventures with Johnny that doesn’t quite make sense but he finds himself actually having fun with whatever Johnny is up to. And Johnny attracts A LOT OF THAT if you know him. (He relaxes a little when he realizes that for whatever reason Aku hasn’t affected this timeline, probably because of Bunny if you read the Grimdark Johnny Bravo Theory) Jack does see that Johnny putting up this mask of Bravado as unnecessary but when Johnny does put it down for those few times/seconds, he finds him quite endearing. He’s sharp enough to know that Johnny is interested in him romantically from the way Johnny makes some exceptions for him (or maybe A LOT haha). But Jack can’t really do anything about it, he’s always had to move on, and he knows that eventually he’ll have to go back to defeat Aku. But somehow the thought of never seeing Johnny again twinges him in a unexpected way but he’ll have to push his feelings away for his destiny. Jack thinks that Johnny will probably forget about him eventually and move on with the numerous ladies he’s attracted to that day. (that doesn’t make Jack feel any better though)
I think that’s about it! It’s pretty sad but yeahhhh…