I often get asked why myCal is adding default alerts to new events. In actual fact it doesn't, but if those events are on a Google calendar then chances are its Google itself that is the cuplrit. Fear not though! There is a solution. Try the following:
- Goto https://calendar.google.com/calendar and login
- Expand the My Calendars section in the left hand panel
- Click the down arrow to the right of the calendar name
- Select Edit Notifications
- Remove any default reminders