The one rule I follow before mixing two worlds
Crossovers are easy to start and easy to ruin. The difference is whether the two worlds actually have a reason to meet.
Dropping Mario into a Pokémon landscape sounds like a five-minute idea. The hard part isn't the mashup — it's making it feel like it belongs, instead of two stickers slapped on the same page.
Pick a host, not a tie
Every crossover I paint has a host world and a guest. Mario visiting Kanto is Mario rendered in Pokémon's light and color logic — not a 50/50 negotiation. When both worlds insist on their own rules, the piece reads as a collage. When one clearly hosts the other, it reads as a place.
Match the lighting before the lore
Fans will forgive almost any story stretch if the light is consistent. A single key light, one shared color temperature, and grounded shadows do more to sell a crossover than any amount of clever reference. Get the photons agreeing and the characters follow.
Keep one anchor recognizable
The guest character should survive the trip. If I restyle Pikachu so hard he could be any yellow creature, the joke and the warmth both evaporate. I'll bend the rendering, never the silhouette.
A good crossover is a small act of worldbuilding. Decide who's hosting, agree on the light, protect the silhouette — then have fun with the rest.