@CM30 From one of the translators with Wario like icon photoshops on twitter, I forgot if his name was PushDustin, who was translating the (now retired) Norio Ohkubo's interview.
It seems the hidden little girl rival you find in Wrecking Crew 98 is based on a Japanese urban legend of a girl who shows and scares anyone using the public bathrooms of a school.
So apparently Mario was planned to be Bomberman's antagonist in Wario's Blast but they changed the idea because it wouldn't fit his character and Wario was already establishing his name during the 90s.
I assume it's a stage parodying Bowser's Japanese castle from Odyssey, but it could also be a reference to Wario Land Shake it. It's a shame Wario's Stadium from N64 will never be remastered.
I remember seeing a guy who breathes, eats, and sleeps Wario World, he had a Youtube channel where he shows how many exploits were fixed in the Japanese version. Does anyone know who am I referring to?