He says that according to what he can reveal me, the joke texture was made during the initial development for PS2/PC ( that kinda explains the low resolution ), but was simply left in the .psd file alongside the valid texture, never exported in the final game.
However, for the XBox 360 port in 2008, an intern was given the job to export the textures in a higher resolution, she wasn't aware of what the original textures supposed to look like and exported into the game the Glenn joke texture out of the .psd.
Martyste Tendertail
Feel free to add to the wiki if you need...
Mr.Rubinshtein
legend
Mr.Rubinshtein
@Martyste Tendertail could you please invest some time and fill in the download sections with your files?