At the start of the game, in the grocery store where all the zombie corpses are, near the exit is a bear.
If you look closely it is the one from the Garfield TV show that was on the Cartoon Network.
Escape (After Credits)
After the end credits have rolled, there is yet more action to be played. You must dash to the Tower of London, ideally avoiding the many zombies scattered along the way. Feel free to use all of your best weapons and ammo, no need to save it for a rainy day. At the top of the steps of the Tower, you'll see the door that was once barricaded is now open, so head inside.
Continue to ignore the majority of zombies as you flee for your life, and make your way up the stairs and through the door at the top, shutting it behind you and boarding it up if you're able to. Head through the next room and take out the zombie guarding the stairs so you can head down them. Once you reach the bottom, take out the zombies coming down the spiral staircase and then head up that. At top waits Sandra with a helicopter, and your freedom.
Letter of Dee Victoria's Memorial Location
In the room where you found the C4 in Victoria's Memorial Hospital you'll also find a dead body lounging rather dead-like against the wall. Loot this body for another Letter of Dee.
Letter of Dee Baconfields
Travel to Baconfields and head for the shed at the far end of the field, killing enemies along the way if they've respawned to the point of nuisance. Use the scanner on the keypad and instead you'll find a corpse with the Letter of Dee on it.
Letter of Dee Brick Lane Flats
Head to the Tower of London, and make your way to the boat docked at the pier. Hack the lock and head down there to confront a super zombie. In the dumpster here you'll find a dead body with another Letter of Dee on it.
Letter of Dee Brick Lane Markets Location
Across from the supermarket in the Brick Lane Markets area, you'll find a set of stairs attached to the apartment building. Underneath these stairs is a cracked wall partially obscured by a pile of rubbish. Place some C4 there to blow that cracked wall to smithereens and search the dead body on the other side of it for the Letter of Dee.
Letter of Dee Spitalfields Green
Travel to Spitalfields Green and make your way to area with mines covering the center of it. You'll need time to hack the keypad door, so kill all the zombies in the area first before proceeding. Now hack the keypad and then scan the CCTV camera box on the side of the building. Through the hole in the wall you'll find a zombie with the Letter of Dee on him.