For the first part, Kamen Rider and Pretty Cure get linked together a lot because:
- Both shows are made by Toei
- Airs around the same time in Japan
- Similar pacing and formula
- Share Writers and Actors
- Bandai uses them to sell toys
So you get a lot of Ads and promotional events where characters from both shows get to interact.
Kamen Rider Wizard and Doki Doki aired at the same time so it was inevitable.
As for the second... Precure movies and mangas can get wild.
Like the Smile Precure girls ( Haruka and Michiru met one of them, Yayoi Mecha fan) have to fight Cinderella, Issun-boshi, Sun Wukong, Taro Urashima and Momotaro in their movie.
Edit: Ok, I just remembered.
So Maho Girls Pretty Cure (Mother Rapapa's season) has an official manga. There is a scene where the 2 main leads kiss. To be fair, it was to force-feed medicine.
However, The leader Cure, Mirai, had to force-feed the medicine to 3 characters. Only her Partner Cure, Riko got special emphasis, the Sparkly background and flashbacks of happy memories. Not to mention how often they get called a family with the kids they have by other characters and the narration