Can we discuss Konspiracies here about King K.Rool's probable 'rejection' for Smash? The fact he was out-prioriticed by other newcomers (due to more relevance, shamefully).
I feel that Bowser's moveset revamps and Bowser Jr.'s existance are both his biggest reasons of exclusion. The way Bowser stands upright is a stance I easily could see K.Rool taking for example. Outside of Bowser's Inside Story, Bowser is always mostly hunched over as in Melee and Brawl.
We've seen that outside of King K.Rool, most biggest requested characters made it in. MegaMan is probably the best example. And he got revealed early in development, just like Bowser. Ridley also has his own reasons for exclusion as we know, but he might be scrapped with K.Rool early on. And as we know, Bowser Jr. almost didn't make the cut.
King K.Rool might've probably either been too similar to Bowser for them to continue development, or he was partly created but scrapped due to lack of recent appearances and other ideas they had to work on (Shulk, Duck Hunt, PacMan, Mii- all rather late additions). Moves I speculate he could have had are: Bowser's F Smash, Bowser Jr's Neutral B, Bowser's Custom Side B, Bowser's new aerials, Charizard's new Forward Air. My base for this theory is Mewtwo's exclusion from Brawl, and Lucario, Lucas, Wolf and Charizard inherriting some moves from him (Neutral B, F Smash, F Air, D Smash, N Air, F Tilt). So it's not like it's the first time this has happened. Villager and Snake sharing similarities is another thing that has got me thinking this.
K.Rool might simply be rejected cause they needed more time for him, or they wanted to include him when they got more to work with due to a new appearance. Bowser Jr. might once have been low priority, but maybe the idea of including all Koopalings and giving him a Side B that references the almighty Mario Kart subseries and Mario Kart 8 needing it's attention made Sakurai focus his attention on Bowser Jr. instead. Not sure how to word this properly but, Bowser Jr. kind of has a playstyle that many expected K.Rool to have. An aggressive zoner, relying on projectiles to get stage control. But Bowser Jr. is a lot lighter, smaller and has his mech of course.
I truely believe K.Rool was once considered as a playable character. It just doesn't make sence that he wouldn't. Not sure if am digging too deep here, but it's fun to speculate about.