diff --git a/tomlkit/container.py b/tomlkit/container.py
index 917a255..9251a98 100644
--- a/tomlkit/container.py
+++ b/tomlkit/container.py
@@ -147,7 +147,19 @@ def _get_last_index_before_table(self) -> int:
             last_index = i
         return last_index + 1
 
-    def append(self, key: Key | str | None, item: Item) -> Container:
+    def _validate_out_of_order_table(self, key: SingleKey | None = None) -> None:
+        if key is None:
+            for k in self._map:
+                assert k is not None
+                self._validate_out_of_order_table(k)
+            return
+        if key not in self._map or not isinstance(self._map[key], tuple):
+            return
+        OutOfOrderTableProxy(self, self._map[key])
+
+    def append(
+        self, key: Key | str | None, item: Item, validate: bool = True
+    ) -> Container:
         """Similar to :meth:`add` but both key and value must be given."""
         if not isinstance(key, Key) and key is not None:
             key = SingleKey(key)
@@ -229,8 +241,8 @@ def append(self, key: Key | str | None, item: Item) -> Container:
                             else:
                                 self._raw_append(key, item)
 
-                            # Building a temporary proxy to check for errors
-                            OutOfOrderTableProxy(self, self._map[key])
+                            if validate:
+                                self._validate_out_of_order_table(key)
 
                             return self
 
@@ -288,7 +300,7 @@ def append(self, key: Key | str | None, item: Item) -> Container:
         self._raw_append(key, item)
         return self
 
-    def _raw_append(self, key: Key, item: Item) -> None:
+    def _raw_append(self, key: Key | None, item: Item) -> None:
         if key in self._map:
             current_idx = self._map[key]
             if not isinstance(current_idx, tuple):
@@ -299,7 +311,7 @@ def _raw_append(self, key: Key, item: Item) -> None:
                 raise KeyAlreadyPresent(key)
 
             self._map[key] = current_idx + (len(self._body),)
-        else:
+        elif key is not None:
             self._map[key] = len(self._body)
 
         self._body.append((key, item))
@@ -607,21 +619,8 @@ def __iter__(self) -> Iterator[str]:
 
     # Dictionary methods
     def __getitem__(self, key: Key | str) -> Item | Container:
-        if not isinstance(key, Key):
-            key = SingleKey(key)
-
-        idx = self._map.get(key)
-        if idx is None:
-            raise NonExistentKey(key)
-
-        if isinstance(idx, tuple):
-            # The item we are getting is an out of order table
-            # so we need a proxy to retrieve the proper objects
-            # from the parent container
-            return OutOfOrderTableProxy(self, idx)
-
-        item = self._body[idx][1]
-        if item.is_boolean():
+        item = self.item(key)
+        if isinstance(item, Item) and item.is_boolean():
             return item.value
 
         return item
@@ -800,11 +799,13 @@ def __init__(self, container: Container, indices: tuple[int]) -> None:
                 self._tables.append(item)
                 table_idx = len(self._tables) - 1
                 for k, v in item.value.body:
-                    self._internal_container.append(k, v)
+                    self._internal_container.append(k, v, validate=False)
                     self._tables_map[k] = table_idx
                     if k is not None:
                         dict.__setitem__(self, k.key, v)
 
+        self._internal_container._validate_out_of_order_table()
+
     def unwrap(self) -> str:
         return self._internal_container.unwrap()
 
diff --git a/tomlkit/items.py b/tomlkit/items.py
index af12ad5..c7396e5 100644
--- a/tomlkit/items.py
+++ b/tomlkit/items.py
@@ -1617,7 +1617,7 @@ def raw_append(self, key: Key | str | None, _item: Any) -> Table:
         if not isinstance(_item, Item):
             _item = item(_item)
 
-        self._value.append(key, _item)
+        self._value.append(key, _item, validate=False)
 
         if isinstance(key, Key):
             key = next(iter(key)).key
diff --git a/tomlkit/parser.py b/tomlkit/parser.py
index bdf0c4a..89ddae2 100644
--- a/tomlkit/parser.py
+++ b/tomlkit/parser.py
@@ -1030,7 +1030,7 @@ def _parse_table(
                         InternalParserError,
                         "_parse_item() returned None on a non-bracket character.",
                     )
-
+        table.value._validate_out_of_order_table()
         if isinstance(result, Null):
             result = table