diff --git a/manimlib/mobject/shape_matchers.py b/manimlib/mobject/shape_matchers.py
index ce0b5097..29551878 100644
--- a/manimlib/mobject/shape_matchers.py
+++ b/manimlib/mobject/shape_matchers.py
@@ -2,50 +2,63 @@ from __future__ import annotations
 
 from colour import Color
 
-from manimlib.constants import BLACK, RED, YELLOW
+from manimlib.constants import BLACK, RED, YELLOW, WHITE
 from manimlib.constants import DL, DOWN, DR, LEFT, RIGHT, UL, UR
 from manimlib.constants import SMALL_BUFF
 from manimlib.mobject.geometry import Line
 from manimlib.mobject.geometry import Rectangle
 from manimlib.mobject.types.vectorized_mobject import VGroup
 from manimlib.mobject.types.vectorized_mobject import VMobject
-from manimlib.utils.config_ops import digest_config
 from manimlib.utils.customization import get_customization
 
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
+    from typing import Sequence
     from manimlib.mobject.mobject import Mobject
     from manimlib.constants import ManimColor
 
 
 class SurroundingRectangle(Rectangle):
-    CONFIG = {
-        "color": YELLOW,
-        "buff": SMALL_BUFF,
-    }
-
-    def __init__(self, mobject: Mobject, **kwargs):
-        digest_config(self, kwargs)
-        kwargs["width"] = mobject.get_width() + 2 * self.buff
-        kwargs["height"] = mobject.get_height() + 2 * self.buff
-        Rectangle.__init__(self, **kwargs)
+    def __init__(
+        self,
+        mobject: Mobject,
+        buff: float = SMALL_BUFF,
+        color: ManimColor = YELLOW,
+        **kwargs
+    ):
+        super().__init__(
+            width=mobject.get_width() + 2 * buff,
+            height=mobject.get_height() + 2 * buff,
+            color=color,
+            **kwargs
+        )
         self.move_to(mobject)
 
 
 class BackgroundRectangle(SurroundingRectangle):
-    CONFIG = {
-        "stroke_width": 0,
-        "stroke_opacity": 0,
-        "fill_opacity": 0.75,
-        "buff": 0
-    }
-
-    def __init__(self, mobject: Mobject, color: ManimColor = None, **kwargs):
+    def __init__(
+        self,
+        mobject: Mobject,
+        color: ManimColor = None,
+        stroke_width: float = 0,
+        stroke_opacity: float = 0,
+        fill_opacity: float = 0.75,
+        buff: float = 0,
+        **kwargs
+    ):
         if color is None:
             color = get_customization()['style']['background_color']
-        SurroundingRectangle.__init__(self, mobject, color=color, **kwargs)
-        self.original_fill_opacity = self.fill_opacity
+        super().__init__(
+            mobject,
+            color=color,
+            stroke_width=stroke_width,
+            stroke_opacity=stroke_opacity,
+            fill_opacity=fill_opacity,
+            buff=buff,
+            **kwargs
+        )
+        self.original_fill_opacity = fill_opacity
 
     def pointwise_become_partial(self, mobject: Mobject, a: float, b: float):
         self.set_fill(opacity=b * self.original_fill_opacity)
@@ -74,27 +87,37 @@ class BackgroundRectangle(SurroundingRectangle):
 
 
 class Cross(VGroup):
-    CONFIG = {
-        "stroke_color": RED,
-        "stroke_width": [0, 6, 0],
-    }
-
-    def __init__(self, mobject: Mobject, **kwargs):
+    def __init__(
+        self,
+        mobject: Mobject,
+        stroke_color: ManimColor = RED,
+        stroke_width: float | Sequence[float] = [0, 6, 0],
+        **kwargs
+    ):
         super().__init__(
             Line(UL, DR),
             Line(UR, DL),
         )
         self.insert_n_curves(20)
         self.replace(mobject, stretch=True)
-        self.set_stroke(self.stroke_color, width=self.stroke_width)
+        self.set_stroke(stroke_color, width=stroke_width)
 
 
 class Underline(Line):
-    CONFIG = {
-        "buff": SMALL_BUFF,
-    }
-
-    def __init__(self, mobject: Mobject, **kwargs):
-        super().__init__(LEFT, RIGHT, **kwargs)
+    def __init__(
+        self,
+        mobject: Mobject,
+        buff: float = SMALL_BUFF,
+        stroke_color=WHITE,
+        stroke_width: float | Sequence[float] = [0, 3, 3, 0],
+        **kwargs
+    ):
+        super().__init__(
+            LEFT, RIGHT,
+            stroke_color=stroke_color,
+            stroke_width=stroke_width,
+            **kwargs
+        )
+        self.insert_n_curves(30)
         self.match_width(mobject)
-        self.next_to(mobject, DOWN, buff=self.buff)
+        self.next_to(mobject, DOWN, buff=buff)