Homsar was originally created only for the second e-mail, but then Matt and Mike decided to keep him around.
The song "Different Town" on email #99 was composed by John Linnell of They Might Be Giants. If you listen to the creators' commentary for that email, you can hear what the original song sounded like.
The first 100 Strong Bad E-Mail shorts were originally released on the Homestar Runner website from August 2001 to March 16, 2004.
All of the cartoons on the DVD were made in Macromedia Flash.