The Red Herring badge was a secret badge that could be found as part of the Northpole Noir Holiday Sale 2015.
To get the badge, follow these steps:
- Go to Ikaruga in the Steam Store
- Simply type "search"
- Press Enter
- Enter the code 1v7531
You will then be redirected to another page where you will get the badge. It is worth 100 xp.