Google automatically adds event invitations to you calendar without telling you which can be really annoying. This even happens if you disable Automatically add invitations to my calendar in Calendar Settings.
To fix this, do the following:
- Open Google Calendar
- Go to Settings (top right) > Calendar Settings > Calendars (tab) > Notifications link (on your primary calendar)
- Tick EMAIL for the first 4 items, click SAVE.
Then to be sure, also set Calendar Settings > Automatically add invitations to my calendar in Calendar Settings to No, only show invitations to which I have responded.