diff --git a/homeassistant/components/demo/fan.py b/homeassistant/components/demo/fan.py
index 89256c95468..e70f5efc626 100644
--- a/homeassistant/components/demo/fan.py
+++ b/homeassistant/components/demo/fan.py
@@ -114,11 +114,11 @@ class BaseDemoFan(FanEntity):
         self.hass = hass
         self._unique_id = unique_id
         self._supported_features = supported_features
-        self._percentage = None
+        self._percentage: int | None = None
         self._preset_modes = preset_modes
-        self._preset_mode = None
-        self._oscillating = None
-        self._direction = None
+        self._preset_mode: str | None = None
+        self._oscillating: bool | None = None
+        self._direction: str | None = None
         self._name = name
         if supported_features & SUPPORT_OSCILLATE:
             self._oscillating = False
@@ -141,12 +141,12 @@ class BaseDemoFan(FanEntity):
         return False
 
     @property
-    def current_direction(self) -> str:
+    def current_direction(self) -> str | None:
         """Fan direction."""
         return self._direction
 
     @property
-    def oscillating(self) -> bool:
+    def oscillating(self) -> bool | None:
         """Oscillating."""
         return self._oscillating
 
@@ -257,7 +257,7 @@ class AsyncDemoPercentageFan(BaseDemoFan, FanEntity):
 
     async def async_set_preset_mode(self, preset_mode: str) -> None:
         """Set new preset mode."""
-        if preset_mode not in self.preset_modes:
+        if self.preset_modes is None or preset_mode not in self.preset_modes:
             raise ValueError(
                 "{preset_mode} is not a valid preset_mode: {self.preset_modes}"
             )
diff --git a/homeassistant/components/demo/light.py b/homeassistant/components/demo/light.py
index 13e15eb274e..9bb3a30686d 100644
--- a/homeassistant/components/demo/light.py
+++ b/homeassistant/components/demo/light.py
@@ -195,17 +195,17 @@ class DemoLight(LightEntity):
         return self._color_mode
 
     @property
-    def hs_color(self) -> tuple:
+    def hs_color(self) -> tuple[float, float]:
         """Return the hs color value."""
         return self._hs_color
 
     @property
-    def rgbw_color(self) -> tuple:
+    def rgbw_color(self) -> tuple[int, int, int, int]:
         """Return the rgbw color value."""
         return self._rgbw_color
 
     @property
-    def rgbww_color(self) -> tuple:
+    def rgbww_color(self) -> tuple[int, int, int, int, int]:
         """Return the rgbww color value."""
         return self._rgbww_color
 
diff --git a/homeassistant/components/demo/number.py b/homeassistant/components/demo/number.py
index dd22c5f9827..8660604af9e 100644
--- a/homeassistant/components/demo/number.py
+++ b/homeassistant/components/demo/number.py
@@ -105,13 +105,10 @@ class DemoNumber(NumberEntity):
         if step is not None:
             self._attr_step = step
 
-    @property
-    def device_info(self) -> DeviceInfo:
-        """Return device info."""
-        return DeviceInfo(
+        self._attr_device_info = DeviceInfo(
             identifiers={
                 # Serial numbers are unique identifiers within a specific domain
-                (DOMAIN, self.unique_id)
+                (DOMAIN, unique_id)
             },
             name=self.name,
         )
diff --git a/homeassistant/components/demo/remote.py b/homeassistant/components/demo/remote.py
index 2e06b009c9c..f2c1ce11b0a 100644
--- a/homeassistant/components/demo/remote.py
+++ b/homeassistant/components/demo/remote.py
@@ -46,7 +46,7 @@ class DemoRemote(RemoteEntity):
         self._attr_name = name or DEVICE_DEFAULT_NAME
         self._attr_is_on = state
         self._attr_icon = icon
-        self._last_command_sent = None
+        self._last_command_sent: str | None = None
 
     @property
     def extra_state_attributes(self) -> dict[str, Any] | None:
diff --git a/homeassistant/components/demo/siren.py b/homeassistant/components/demo/siren.py
index 32d3de4b497..9cf18a4c902 100644
--- a/homeassistant/components/demo/siren.py
+++ b/homeassistant/components/demo/siren.py
@@ -54,7 +54,7 @@ class DemoSiren(SirenEntity):
     def __init__(
         self,
         name: str,
-        available_tones: str | None = None,
+        available_tones: list[str | int] | None = None,
         support_volume_set: bool = False,
         support_duration: bool = False,
         is_on: bool = True,
diff --git a/homeassistant/components/demo/switch.py b/homeassistant/components/demo/switch.py
index c61e39d085b..217119e9372 100644
--- a/homeassistant/components/demo/switch.py
+++ b/homeassistant/components/demo/switch.py
@@ -64,12 +64,8 @@ class DemoSwitch(SwitchEntity):
         self._attr_is_on = state
         self._attr_name = name or DEVICE_DEFAULT_NAME
         self._attr_unique_id = unique_id
-
-    @property
-    def device_info(self) -> DeviceInfo:
-        """Return device info."""
-        return DeviceInfo(
-            identifiers={(DOMAIN, self.unique_id)},
+        self._attr_device_info = DeviceInfo(
+            identifiers={(DOMAIN, unique_id)},
             name=self.name,
         )
 
diff --git a/mypy.ini b/mypy.ini
index c5afffd5638..2ad49bfdc4c 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -2196,24 +2196,6 @@ ignore_errors = true
 [mypy-homeassistant.components.deconz.switch]
 ignore_errors = true
 
-[mypy-homeassistant.components.demo.fan]
-ignore_errors = true
-
-[mypy-homeassistant.components.demo.light]
-ignore_errors = true
-
-[mypy-homeassistant.components.demo.number]
-ignore_errors = true
-
-[mypy-homeassistant.components.demo.remote]
-ignore_errors = true
-
-[mypy-homeassistant.components.demo.siren]
-ignore_errors = true
-
-[mypy-homeassistant.components.demo.switch]
-ignore_errors = true
-
 [mypy-homeassistant.components.denonavr.config_flow]
 ignore_errors = true
 
diff --git a/script/hassfest/mypy_config.py b/script/hassfest/mypy_config.py
index 376f33de65b..f776f1b635b 100644
--- a/script/hassfest/mypy_config.py
+++ b/script/hassfest/mypy_config.py
@@ -38,12 +38,6 @@ IGNORED_MODULES: Final[list[str]] = [
     "homeassistant.components.deconz.services",
     "homeassistant.components.deconz.siren",
     "homeassistant.components.deconz.switch",
-    "homeassistant.components.demo.fan",
-    "homeassistant.components.demo.light",
-    "homeassistant.components.demo.number",
-    "homeassistant.components.demo.remote",
-    "homeassistant.components.demo.siren",
-    "homeassistant.components.demo.switch",
     "homeassistant.components.denonavr.config_flow",
     "homeassistant.components.denonavr.media_player",
     "homeassistant.components.denonavr.receiver",