Names in the Mega Man series change quite frequently, such that a character is known as one thing in one game and by something else somewhere else. This confuses people new to the series who sometimes have no idea who someone is talking about, or think that the games have a bunch of clones of certain characters running around.

Most, although not all, of these name changes are a result of the fact that the games are made in Japanese first, then translated later into English. This causes several problems and mix-ups which are listed below.

The following chart lists only name changes that have some applicable commentary. There are many more (for example, virtually every Maverick in the X series has undergone at least one name change, and most of the Battle Network/Star Force characters have name changes); the games’ respective Data Base pages document these changes. (Look for the “Also Known As” tags.)

For a list of the musical names found throughout the series, see the separate page.

RockmanMega ManAccording to people at Capcom, it seems someone thought “Rock Man” didn’t sound heroic enough...or something. (See the commentary on this for more elaboration.)
Proto Man
Break Man
I suppose the name “Blues” was changed due to the fact that he’s not blue, even though the name is a reference to music, not color. It is interesting to note that the name “Break Man” is common to both languages.
Dr. Light
Dr. Right
Dr. Light
Dr. Right
Dr. Wright
There is no “L” sound in Japanese so “R” is used as an approximation. Thus, to Japanese the names “Right” and “Light” are the exact same thing; therefore they are used quite interchangeably. This trend tends to carry over to the English games on occasion. Additionally, the spelling “Dr. Wright” was used in one English game, Mega Man 1 (most likely chosen because “Wright” is a real last name), but was subsequently dropped.
Dr. Wily
Dr. Waily
Dr. Wily
Dr. Wiley
Dr. Willy
I have no information on why Dr. Wily’s name has changed spellings, only speculation (I still think his middle name is Wiley...). It’s possible some translators, not aware of the proper spellings, decided to use “Wiley” because that is a real name, whereas “Wily” is not (although “wily” is a word). The last name listed (Willy) was undoubtedly merely a typo. (Why “Waily”? Because in Japanese that’s technically how the name is spelled. Usually when Japanese use English characters to write the name, they spell it “Wily” but sometimes they forget.)
ForteBassThis was a simple name change that, as with Mega Man, seemed to have no reason other than to do it. I do admit however that “Bass” and “Treble” do seem to go together better when taken as a pair.
GospelTrebleThis is a more obscure one that most people are unaware of. Why they named him Gospel in Japan is anyone’s guess. (It is a musical term, but otherwise, it has nothing to do with Forte. Why wasn’t Gospel named Piano?)
LanAgain, since this name was already in English, I’m baffled as to why Capcom felt compelled to change it. As a side note, Lan’s name in Japanese is actually a play on words, which, according to the experts I asked, is obvious to anyone who can speak Japanese, but unfortunately doesn’t work in English. Basically, the writers took the English word “Net” (which is pronounced “netto” due to the way the Japanese language is spoken) and found kanji which have the same pronounciation to use as his name. They also played the same double-meaning trick for a couple other characters. (Side note: Yes, I know that LAN = Local Area Network. I found this to be so obvious that I didn’t think I even had to mention it. But due to the number of e-mails I’ve received, I guess have to add a note on it...)
At first it seemed that Capcom was going to rename Eddie to “Flip-Top” in English. Then, however, they dumped this idea and began calling him “Eddie” even in English. No word as to why.
Crash Man
Clash Man
Again, since “L” and “R” are synonymous to each other in Japanese, this name gets altered a few times throughout the series, even in English. This trend also affects weapon names and such.
EarthTerraThe robots from this game were all named around planets or other features of the solar system. Since the other eight* planets were there (the game was written before Pluto was demoted), it only makes sense for Earth to be included. “Terra” is a word that relates to Earth; however, it is unknown why the name was changed. (What they really should have used was “Tera Man” heh heh...)
SungodSunstarRemember the old Nintendo rules (which have since been dropped, but the effects of them can still be seen in old games) dictating that no games on Nintendo systems in America could make references to religious terms? This is evidently the reason behind the changes of such names as Sungod, Yellow Devil, and Gospel.
My guess is this name was changed because in Japanese, “B” is the same as “V” and thus “Vava” could also be thought of as “Baba” and “Baba” is just a little too close to Boba (as in, Boba Fett). I think Capcom probably figured Vile’s appearance was close enough and decided not to rub in the association. (For some reason, ripping off Star Wars is okay in Japan, but not in America... For example, I’ve heard that Zero’s sabre sounded just like a lightsaber in the Japanese games but was changed to a different sound in—you guessed it—the English games. I suppose they think no one who works on Star Wars ever plays Japanese games?) Someone forgot for the translation of Xtreme however, as this game marks the first English game to use the name Vava. (See the commentary on this for more discussions.)