Pay close attention to the rules of the page. By default, only "Name" and "E-mail" fields are required. However, as soon as you select a "Favorite Sport" the "Favorite Team" becomes required. Selecting any sport, except "Other", will force you to select a team from the list of valid professional teams. The "Other" and "Favorite Team" input boxes are disabled by default.
If you select "Other" as your favorite sport, then you're required to fill in the "Other" input box as well as manually type in your "Favorite Team." If a value is entered in the "Other" text box and then a different sport is selecting, the value in the "Other" input box is cleared. However, reselecting the "Other" option will repopulate the "Other" input box with the lastValue property of the field.