diff --git a/app/models.py b/app/models.py
index fbe1bd7..750ed16 100644
--- a/app/models.py
+++ b/app/models.py
@@ -9,8 +9,12 @@
 class Clone(db.Document):
     created_at = db.DateTimeField(default=datetime.datetime.now, required=True)
     username = db.StringField(required=True, unique=True)
-    patterns = db.ListField(db.StringField(), required=True)
-    vocabulary = db.DictField(required=True)
+
+    # Mad-lib Tweet patterns.
+    patterns = db.ListField(db.StringField(), required=True, default=[])
+
+    # { POS tag: words }
+    vocabulary = db.DictField(required=True, default={})
 
     meta = {
             'allow_inheritance': True,
@@ -18,18 +22,11 @@ class Clone(db.Document):
             'ordering': ['-created_at']
     }
 
-    def imprint(self, username):
+    def imprint(self):
         """
         Generate a clone for a given Twitter user.
         """
-        self.username = username
-        user_tweets = twitter.tweets(username, count=2000)
-
-        # { POS tag: words }
-        self.vocabulary = {}
-
-        # Mad-lib Tweet patterns.
-        self.patterns = []
+        user_tweets = twitter.tweets(self.username, count=2000)
 
         for tweet in user_tweets:
             text = tweet['body']
diff --git a/app/routes/clones.py b/app/routes/clones.py
index 0844104..62041f4 100644
--- a/app/routes/clones.py
+++ b/app/routes/clones.py
@@ -16,7 +16,7 @@ def clones():
     if form.validate_on_submit():
         username = form.username.data
         clone = Clone.objects.get_or_create(username=username)
-        clone.imprint(username)
+        clone.imprint()
         clone.save()
         return redirect(url_for('clones.clone', username=username))
     return render_template('clones/create.jade', form=form)