Ah entonces lo hicieron con el Visage nomás...
OS X Hints tiene un tutorial distinto para el Tiger:
With the release of Tiger, the window that reads "Starting Mac OS X..." (which appears just before the login window) has been changed to a "fake" window (see this hint). This window no longer shows what is actually happening, it just has generic text that is now possible to change, if you are willing to enable the root account (this can be done by opening NetInfo Manager, which is located in Utilities, and visiting the Security menu).
Once you've enabled the root account, browse to /System -> Library -> CoreServices -> Resources. There will be a number of different folders for different languages. Choose the one that your system uses when it boots up (probably English.lproj). If you have the Xcode Developer Tools installed, just open the file called SystemStarterUI.strings. Otherwise, it should be possible to edit it in TextEdit.
On the second line, it should say:
"SYSTEM_STARTING_MESSAGE" = "Starting Mac OS X...";
Where it says "Starting Mac OS X...," put in your own message (leave the quotation marks around your message). I wouldn't reccomend putting in anything strange like nothing at all, paragraphs of text, weird symbols, etc. (although I honestly haven't experimented with all the possible things you could put in there), but you can try.
After you've done your edits, save the file, log out of root, disable root if you want, and then restart your Mac. When it boots, the text that goes along with the progress bar should say your personalised message instead of "Starting Mac OS X..."
[robg adds: You do not need to enable nor login as root to edit this file. Instead, simply drag it to your desktop -- OS X will create a copy, since you don't have the rights to move the file. Open the copy on your desktop, make the edits, and save the file. When you're done, quit the editor, and drag the file back to its original location. OS X will ask you to authenticate (provide your admin password), and then ask if you want to overwrite the file. Say yes, and you're done. You should probably keep an unedited copy around, too, just in case...]
MacBook Pro Retina 15" + MacBook Air M2 15” + Apple Studio Display 27" + Apple Thunderbolt Display 27" + iPhone 14 Pro + iPad 2 + Newton 100
"Iguana iguana Powersurgius"