So, some backstory:
Problem: Gamers online often debate what game developers were thinking when they made certain choices for games they love. They often do this with absolutely no insight into the thought processes of those developers.
Solution: A gamer who can translate Japanese made a website called Shmuplations.com where he finds old interviews with the actual developers themselves, posting their translated words so gamers can understand the actual thought processes.

A few days ago, the site posted an interview from the November 2002 issue of Nintendo Dream, between Shigehisa Nakaue and Takaya Imamura, discussing things about the Star Fox series development and Star Fox Adventures specifically. Shigehisa Nakaue co-developed the Star Fox Adventures Prequel Manga, and would later join Nintendo himself. Takaya Imamura, for those who don't remember, just retired from Nintendo in January, but over his career he was known for character design of the Star Fox characters and helping manage those games. The entire article is worth a read.

Read the Interview Now!

In the interview, a discussion was had about Krystal. Among the points, the following Krystal and Adventures facts came to light:

• Fox ultimately used Krystal's staff instead of a gun, sword, or whip because it was a more blunt weapon and would get around content problems related to cutting/slashing.
• Imamura's favorite character in Star Fox Adventures is Krystal.
• He personally did a lot of Krystal sketches and pushed for her to remain in the game as it was changed from Dinosaur Planet to Star Fox Adventures. (It was already known that Krystal was possibly going to be cut during the transition.)
• Some of those sketches took influence from a risque vampire character named Vampirella, from a comic series of the same name.
• Both Imamura and Miyamoto both thought Krystal should have more sex appeal.
• Miyamoto always saw Star Fox as a serious sci-fi story, not a campy or humorous one. Part of making Krystal more sexy had to do with this desire for the series. Mature elements without going too far.
• Katt Monroe might have been a previous attempt at this, but Imamura thinks that Krystal handles the role better.
• Krystal is the first female Rare character that Shigehisa Nakaue really liked.
• Imamura considers Krystal the heroine of Star Fox Adventures.
• Imamura tried to make Krystal's design stand out to Japanese people specifically, while also making her look like she belonged with the rest of the Star Fox characters.
• Nintendo was already working with Namco on the next Star Fox game, so there's some discussion about that, as well as interest in making another Star Fox Adventures-style game.