Top 5 License Pitches That Failed - VGFacts Top Lists
In 2011, Udon Entertaiment pitched the idea of a "Darkstalkers HD" remake, which would be similar to Udon's previous work of Super Street Fighter II Turbo HD Remix. The pitch was rejected because Capcom wanted to focus Darkstalkers Resurrection, a collection of the second and third games in the series.
Contributed by ZpaceJ0ck0
According to a 1994 Gamest magazine interview with the game's planner Junichi Ohno, he was asked what made him want to make a fighting game where every character was a monster? He responded:

"One reason, as you can probably guess, is that we wanted to create a new, different style of versus fighting game. In the midst of our brainstorming, someone proposed, well, why not make it all about monsters then? With monsters, we wouldn’t have to create brand new characters from wholecloth, and we could use famous monster characters that people would already be familiar with."

As Darkstalkers: The Night Warriors was a brand new fighting game, Ohno and his team also wanted to create brand new special moves for the monsters that were different from those from the Street Fighter II series.
Contributed by ProtoSnake
In a 1994 interview with the game's planner Junichi Ohno & Capcom producer Noritaka Funamizu published in Gamest magazine, they stated that they considered putting monsters from all regions in the series. From the beginning, there were lots of yōkai (traditional Japanese monsters), but they cut the number of them down due to the team realizing that most international players would not recognize them.

Some "weird" characters from the beginning of Darkstalkers: The Night Warriors' development that were rejected include:
•An old man who was dressed head-to-toe in a salaryman’s suit.
•A nurikabe yōkai that could not move and was always in a guard state, which the game's planners mentioned would be easy to finish due to there being little about the character to animate.
•An Invisible Man where the only thing about it the player would be able to see was his floating gloves, which was done so the development team could draw fewer graphics.
Contributed by ProtoSnake
During the early stages of development, Lilith was meant to be a "male daughter" (Japanese term used to describe a man who dresses as if they were woman, known in the western world as a cross-dresser), as Lilith was designed to complement Morrigan. There was also a possible idea to have her gender labeled "unknown."
Contributed by DrakeVagabond
Many of the characters in the series are references to famous movie monsters and their actors, ancient mythical creatures, and gods.
Contributed by gamemaster1991