From the Main Menu select the new unlocked characters either the Toy Robot, or the Scarecrow and the Farmer, also you will see behind the kissing tire you now have the Elf Hat unlocked.
The entire week that you play all the characters will be unlocked to whoever plays the game.
Horde Mode has been edited to allow for single players to start the game alone, simply run outside and the game will begin. In addition at Wave 10 a new character unlocks (scarecrow) and at Wave 20 the (robot unlocks) for those that miss the weekend special.