Dooper is a popular low poly VTuber, introduced into friends vs friends in the Expensive Update.

His personality card is called Determination. Determination adds a Beserker card to your hand each round. The card depicts Dooper holding a photo of... Woman....

To unlock Dooper, you must first unlock the secret character Dingo.

To unlock FNF_Dingo, equip the 404 card and the Parly card into your deck. Then join a woods map. I would recommend trying this in a private game with a friend, as you cannot play the woods map with bots. When in the map, you must have both cards in your deck in a single round. Head inside of the cabin, then use the 404 card followed by the Parley card. If done correctly, you will unlock FKF_Dingo.

Now you have unlocked FKF_Dingo, you can unlock Dooper.

To unlock Dooper, play 60 matches with FKF_Dingo. I recommend playing singles for quicker games.

Dooper: https://x.com/Dooper64
FKF_Dingo: https://friends-vs-friends.fandom.com/wiki/FKF_Dingo