Talk:Fan: Half-life theory/@comment-25867149-20150507144552/@comment-74.40.99.185-20150509234810

There are two reasons that L4D is apart of the Half Life lore:

Dr. Breen appears on a newspaper

That massive Portal easter egg (GLaDOS making you fight zombies)

There isn't any proof that Headcrab zombies are the only zombies.