diff --git a/demos/README.md b/demos/README.md
index a9f8c2bf..674a7f5c 100644
--- a/demos/README.md
+++ b/demos/README.md
@@ -50,6 +50,7 @@ You can see the valid command line args for a demo with:
 
 The parameters general to all demos are listed here:
 
+    --world     (str): (Optional) World to use for demo (Bullet or Real). If not defined, spec from config yaml file is used.
     --ctrl_type (str): Controller type for the demo.
     --demo_type (str): Type of demo to perform.
     --test_fn (str): RobotInterface function environment will use to perform actions. Specific to controller type.
diff --git a/demos/demo.py b/demos/demo.py
index ee7d8311..f428d338 100644
--- a/demos/demo.py
+++ b/demos/demo.py
@@ -42,6 +42,9 @@ def __init__(self,
         # Overwrite config file controlType
         self.config = YamlConfig(self.config_file)
         self.config['world']['controlType'] = self.ctrl_type
+        # Use command line argument over the config spec. 
+        if kwargs['world'] is not None: 
+            self.config['world']['type'] = kwargs['world']
 
         self.demo_type = demo_type
         self.test_fn = test_fn
diff --git a/demos/run_gc_demo.py b/demos/run_gc_demo.py
index 5e7142c0..a42e9f4c 100644
--- a/demos/run_gc_demo.py
+++ b/demos/run_gc_demo.py
@@ -8,7 +8,8 @@
 
 parser = argparse.ArgumentParser(
     description="Test controllers and measure errors.")
-
+parser.add_argument('--world', default=None, 
+     help='World type for the demo, uses config file if not specified', choices=['Bullet', 'Real'])
 parser.add_argument('--num_steps', default=500, type=int,
                     help="max steps for demo.")
 parser.add_argument('--plot_pos', action="store_true",
diff --git a/demos/run_jointimp_demo.py b/demos/run_jointimp_demo.py
index 41b9a3c3..895326b0 100644
--- a/demos/run_jointimp_demo.py
+++ b/demos/run_jointimp_demo.py
@@ -5,6 +5,8 @@
 
 parser = argparse.ArgumentParser(
     description="Test controllers and measure errors.")
+parser.add_argument('--world', default=None, help='World type for the demo, uses config file if not specified', choices=['Bullet', 'Real'])
+
 parser.add_argument('--delta_val',
                     default=0.01, type=float,
                     help="Max step size (m or rad) to take for demo.")
diff --git a/demos/run_osc_line_demo.py b/demos/run_osc_line_demo.py
index f66232d1..89fcc16a 100644
--- a/demos/run_osc_line_demo.py
+++ b/demos/run_osc_line_demo.py
@@ -7,6 +7,7 @@
 
 parser = argparse.ArgumentParser(
     description="Run OpSpace Line Demo in XYZ directions")
+parser.add_argument('--world', default=None, help='World type for the demo, uses config file if not specified', choices=['Bullet', 'Real'])
 parser.add_argument('--ctrl_type',
                     default="EEImpedance",
                     help='Type of controller to test',
diff --git a/demos/run_osc_rot_demo.py b/demos/run_osc_rot_demo.py
index 1c628c3e..7499e1fc 100644
--- a/demos/run_osc_rot_demo.py
+++ b/demos/run_osc_rot_demo.py
@@ -7,6 +7,8 @@
 
 parser = argparse.ArgumentParser(
     description="Run OpSpace Line Demo in XYZ directions")
+parser.add_argument('--world', default=None, help='World type for the demo, uses config file if not specified', choices=['Bullet', 'Real'])
+
 parser.add_argument('--ctrl_type',
                     default="EEImpedance",
                     help='Type of controller to test',
diff --git a/demos/run_osc_square_demo.py b/demos/run_osc_square_demo.py
index 02f5b693..760b7696 100644
--- a/demos/run_osc_square_demo.py
+++ b/demos/run_osc_square_demo.py
@@ -6,6 +6,9 @@
 
 parser = argparse.ArgumentParser(
     description="Run OpSpace Square Demo ")
+parser.add_argument('--world', default=None, 
+     help='World type for the demo, uses config file if not specified', choices=['Bullet', 'Real'])
+
 parser.add_argument('--ctrl_type',
                     default="EEImpedance",
                     help='Type of controller to test',