diff --git a/moviepy/Clip.py b/moviepy/Clip.py
index fbab136af..efdfb22c6 100644
--- a/moviepy/Clip.py
+++ b/moviepy/Clip.py
@@ -94,7 +94,7 @@ def get_frame(self, t):
         else:
             return self.make_frame(t)
 
-    def fl(self, fun, apply_to=[], keep_duration=True):
+    def fl(self, fun, apply_to=None, keep_duration=True):
         """ General processing of a clip.
 
         Returns a new Clip whose frames are a transformation
@@ -131,6 +131,8 @@ def fl(self, fun, apply_to=[], keep_duration=True):
         >>> newclip = clip.fl(fl, apply_to='mask')
         
         """
+        if apply_to is None:
+            apply_to = []
 
         #mf = copy(self.make_frame)
         newclip = self.set_make_frame(lambda t: fun(self.get_frame, t))
@@ -153,7 +155,7 @@ def fl(self, fun, apply_to=[], keep_duration=True):
 
     
     
-    def fl_time(self, t_func, apply_to=[], keep_duration=False):
+    def fl_time(self, t_func, apply_to=None, keep_duration=False):
         """
         Returns a Clip instance playing the content of the current clip
         but with a modified timeline, time ``t`` being replaced by another
@@ -184,6 +186,8 @@ def fl_time(self, t_func, apply_to=[], keep_duration=False):
         >>> newclip = clip.fl_time(lambda: 3-t)
         
         """
+        if apply_to is None:
+            apply_to = []
         
         return self.fl(lambda gf, t: gf(t_func(t)), apply_to,
                                     keep_duration=keep_duration)
diff --git a/moviepy/config.py b/moviepy/config.py
index 307abf901..e102253f8 100644
--- a/moviepy/config.py
+++ b/moviepy/config.py
@@ -80,8 +80,10 @@ def get_setting(varname):
     return gl[varname]
 
 
-def change_settings(new_settings={}, file=None):
+def change_settings(new_settings=None, file=None):
     """ Changes the value of configuration variables."""
+    if new_settings is None:
+        new_settings = {}
     gl = globals()
     if file is not None:
         execfile(file)
diff --git a/moviepy/video/VideoClip.py b/moviepy/video/VideoClip.py
index b1c9089d7..28caf7d19 100644
--- a/moviepy/video/VideoClip.py
+++ b/moviepy/video/VideoClip.py
@@ -489,11 +489,13 @@ def subfx(self, fx, ta=0, tb=None, **kwargs):
 
     # IMAGE FILTERS
 
-    def fl_image(self, image_func, apply_to=[]):
+    def fl_image(self, image_func, apply_to=None):
         """
         Modifies the images of a clip by replacing the frame
         `get_frame(t)` by another frame,  `image_func(get_frame(t))`
         """
+        if apply_to is None:
+            apply_to = []
         return self.fl(lambda gf, t: image_func(gf(t)), apply_to)
 
     # --------------------------------------------------------------
@@ -918,12 +920,14 @@ def __init__(self, img, ismask=False, transparent=True,
         self.size = img.shape[:2][::-1]
         self.img = img
 
-    def fl(self, fl, apply_to=[], keep_duration=True):
+    def fl(self, fl, apply_to=None, keep_duration=True):
         """General transformation filter.
 
         Equivalent to VideoClip.fl . The result is no more an
         ImageClip, it has the class VideoClip (since it may be animated)
         """
+        if apply_to is None:
+            apply_to = []
         # When we use fl on an image clip it may become animated.
         # Therefore the result is not an ImageClip, just a VideoClip.
         newclip = VideoClip.fl(self, fl, apply_to=apply_to,
@@ -932,13 +936,15 @@ def fl(self, fl, apply_to=[], keep_duration=True):
         return newclip
 
     @outplace
-    def fl_image(self, image_func, apply_to=[]):
+    def fl_image(self, image_func, apply_to=None):
         """Image-transformation filter.
 
         Does the same as VideoClip.fl_image, but for ImageClip the
         tranformed clip is computed once and for all at the beginning,
         and not for each 'frame'.
         """
+        if apply_to is None:
+                apply_to = []
         arr = image_func(self.get_frame(0))
         self.size = arr.shape[:2][::-1]
         self.make_frame = lambda t: arr
@@ -952,7 +958,7 @@ def fl_image(self, image_func, apply_to=[]):
                     setattr(self, attr, new_a)
 
     @outplace
-    def fl_time(self, time_func, apply_to=['mask', 'audio'],
+    def fl_time(self, time_func, apply_to=None,
                 keep_duration=False):
         """Time-transformation filter.
 
@@ -962,6 +968,8 @@ def fl_time(self, time_func, apply_to=['mask', 'audio'],
         This method does nothing for ImageClips (but it may affect their
         masks or their audios). The result is still an ImageClip.
         """
+        if apply_to is None:
+                apply_to = ['mask', 'audio']
         for attr in apply_to:
             if hasattr(self, attr):
                 a = getattr(self, attr)
diff --git a/moviepy/video/fx/blackwhite.py b/moviepy/video/fx/blackwhite.py
index 5d4f12399..140c649c6 100644
--- a/moviepy/video/fx/blackwhite.py
+++ b/moviepy/video/fx/blackwhite.py
@@ -1,11 +1,13 @@
 import numpy as np
 
-def blackwhite(clip, RGB = [1,1,1], preserve_luminosity=True):
+def blackwhite(clip, RGB = None, preserve_luminosity=True):
     """ Desaturates the picture, makes it black and white.
     Parameter RGB allows to set weights for the different color
     channels.
     If RBG is 'CRT_phosphor' a special set of values is used.
     preserve_luminosity maintains the sum of RGB to 1."""
+    if RGB is None:
+        RGB = [1,1,1]
 
     if RGB == 'CRT_phosphor':
         RGB = [0.2125, 0.7154, 0.0721]
diff --git a/moviepy/video/fx/mask_color.py b/moviepy/video/fx/mask_color.py
index 8cd302365..b5c102d88 100644
--- a/moviepy/video/fx/mask_color.py
+++ b/moviepy/video/fx/mask_color.py
@@ -1,6 +1,6 @@
 import numpy as np
 
-def mask_color(clip, color=[0,0,0], thr=0, s=1):
+def mask_color(clip, color=None, thr=0, s=1):
     """ Returns a new clip with a mask for transparency where the original
     clip is of the given color.
 
@@ -12,6 +12,8 @@ def mask_color(clip, color=[0,0,0], thr=0, s=1):
     which is 1 when d>>thr and 0 for d<<thr, the stiffness of the effect being
     parametrized by s
     """
+    if color is None:
+        color = [0,0,0]
 
     # code a little sloppy, it just works.
     hill = lambda x: (1.0*(x!=0) if (thr==0) else (x**s/ (thr**s+x**s)))
diff --git a/moviepy/video/tools/drawing.py b/moviepy/video/tools/drawing.py
index 7be3bd093..b398708c6 100644
--- a/moviepy/video/tools/drawing.py
+++ b/moviepy/video/tools/drawing.py
@@ -5,13 +5,15 @@
 
 import numpy as np
 
-def blit(im1, im2, pos=[0, 0], mask=None, ismask=False):
+def blit(im1, im2, pos=None, mask=None, ismask=False):
     """ Blit an image over another.
     
     Blits ``im1`` on ``im2`` as position ``pos=(x,y)``, using the
     ``mask`` if provided. If ``im1`` and ``im2`` are mask pictures
     (2D float arrays) then ``ismask`` must be ``True``.
     """
+    if pos is None:
+        pos = [0, 0]
 
     # xp1,yp1,xp2,yp2 = blit area on im2
     # x1,y1,x2,y2 = area of im1 to blit on im2