Ken's surname is officially Masters, added after Capcom began producing Street Fighter action figures and were sued for copyright infringement by Mattel, the makers of Barbie and Ken dolls. In order to differentiate Street Fighter Ken from Barbie's boyfriend, Capcom U.S.A. added the surname, derived from his 'mastery' of the fighting arts. This is depicted loudly on the side of his yacht in 2nd Impact, along with portraits of himself and his wife, Eliza. Ken's first name stems from one possible pronunciation of the kanji for 'fist', as confirmed by Street Fighter planner 'Finish' Hiroshi Matsumoto in the SF25 retrospective artbook.
Dan Hibiki, introduced in Warriors' Dreams, was created in retaliation to the SNK characters Ryo Sakazaki and Robert Garcia who feature in both the Art of Fighting and King of Fighters series. Ryo in particular was designed to capitalise on the popularity of Street Fighter II's Ryu and Ken; his appearance, fighting style, even his name borrow flagrantly from Capcom's trademarks. To parody SNK, Capcom introduced Dan, a feeble and delusional fighter whose appearance is a cross between Ryo and Robert. One of Dan's win quotes in Alpha 3 makes knowing reference to the mimicry:
I hate the art of fighting, but I wanna be the king of fighters!
Sagat owes the enormous scar on his chest to Ryu's Metsu Shoryuken, the devastating uppercut that finished the first Street Fighter tournament. What is less commonly known is that he lost his right eye some time before to Go Hibiki, who is none other than Dan's father. Go died from his own injuries shortly after the fight and Dan fights with a tragi-comic futility to avenge his father's death. In his Warriors' Dreams and Alpha 2 endings Dan does indeed defeat Sagat, but if this did happen Sagat was merely humoring him and allowed him to win. The rare image of a young Sagat with both eyes intact was drawn by Bengus in promotion of Warrior's Dreams.
The heaviest fighter, for which Capcom have given data, is Hugo at 200 kg. He is also the tallest fighter at 240 cm. On the other end of the scale, Ingrid (exclusive to Street Fighter Alpha 3 MAX) is the lightest and shortest at just 39 kg and 152 cm (according to her in-game profile). Hugo is part of the Andore wrestling family that first appeared in Final Fight and his appearance (and indeed the family name) is based on real-life professional wrestler Andre the Giant. The picture here (from Secret File #16, a promotional magazine distributed in Japan with Street Fighter III: 3rd Strike) can be spotted in the background of his stage in 3rd Strike and casts Hugo as King Kong.
Zangief and Vega have highly divergent views on what constitutes physical perfection. Naturally this is reflected in their own body types and fighting styles and it is addressed directly in Zangief's ending to Super Street Fighter II Turbo. The sequence concludes with an image of the Russian posturing infront of a mirror attached to which is a picture of Vega. The characters scribbled in Japanese on the photo translate as, 'Idiot'! Somewhat on a tangent, the illustrations used to conclude the Super Turbo endings are colourised versions of those drawn by Capcom Design Studio and first published in Gamest magazine, circa September/October 1993.
From Street Fighter, through all iterations of Street Fighter II and the Alpha series, Sagat's eye patch moves from right to left depending on which side he is facing. This is due to technological limitations imposing the use of mirrored sprites. It also explains why Guile has tatoos of the flag of the United States of America on both his arms and why the text on Dee Jay's trousers reads 'MAXIMUM' (a word which appears the same mirrored, unlike the word 'MANTIS', which was originally intended). By the time that Street Fighter III: New Generation was released technology had improved such that characters could now have unique left and right aspects. Gill's blue and red colour scheme was designed in part to demonstrate this advance. Note, however, that Oro can be seen very quickly switching which arm he has bound up when he switches sides, a clever solution by Capcom to avoid the need to draw unique right- and left-facing sprites for Oro whilst still being comprehensible.
Birdie holds the bizarre distinction of being the only Street Fighter character to completely change race from one appearance to the next! In Street Fighter he is clearly white but when his design was updated for inclusion in Warriors' Dreams he became black, whilst the rest of his design remained essentially the same. Capcom knowingly referenced this barefaced change in Secret File #16 (see picture) and playfully in one of his Alpha 3 win quotes:
Oh, what!? ... Before? I looked pale because I was sick!!