If it is based on a real baseball team (and they didn't just make it up) it could be based off the LA dodgers
Not 100% but their logo is always blue and white. It usually has a red baseball above too, but I couldn't find an image that was a reasonable size. The D is very similar writing style to Clem's hat, just slightly altered. The dodgers symbol is generally "LA" in weird letters, but due to copyright they may have just gone with the "D" (with the slight writing alteration). Just a guess!
Comments
The d stands for "d"
Javier said that he remembered that team. Its probably the first letter of a baseball team
The hat used to spell out 'Ed' but the 'E' fell off.
If it is based on a real baseball team (and they didn't just make it up) it could be based off the LA dodgers
Not 100% but their logo is always blue and white. It usually has a red baseball above too, but I couldn't find an image that was a reasonable size. The D is very similar writing style to Clem's hat, just slightly altered. The dodgers symbol is generally "LA" in weird letters, but due to copyright they may have just gone with the "D" (with the slight writing alteration). Just a guess!
The 'D' stands for "Don't necrobump old threads."