diff --git a/lib/compiler/implementation/js_backend/emitter.dart b/lib/compiler/implementation/js_backend/emitter.dart
index cd3132bcce6..41fe157a776 100644
--- a/lib/compiler/implementation/js_backend/emitter.dart
+++ b/lib/compiler/implementation/js_backend/emitter.dart
@@ -1293,8 +1293,7 @@ $classesCollector.$mangledName = {'':
     }
 
     // TODO(ngeoffray): These globals are currently required by the isolate
-    // library, but since leg already generates code on an Isolate object, they
-    // are not really needed. We should remove them once Leg replaces Frog.
+    // library. They should be removed.
     buffer.add("""
 var \$globalThis = $currentIsolate;
 var \$globalState;
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index 530f4cfc7ef..6750f6de210 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -2297,10 +2297,9 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         typeInfo = pop();
       }
       if (type.element.isTypeVariable()) {
-        // TODO(karlklose): We emulate the behavior of the old frog
-        // compiler and answer true to any is check involving a type variable
-        // -- both is T and is !T -- until we have a proper implementation of
-        // reified generics.
+        // TODO(karlklose): We currently answer true to any is check 
+        // involving a type variable -- both is T and is !T -- until 
+        // we have a proper implementation of reified generics.
         stack.add(graph.addConstantBool(true, constantSystem));
       } else {
         HInstruction instruction;
diff --git a/lib/isolate/base.dart b/lib/isolate/base.dart
index 444015ef9f4..0577ec29377 100644
--- a/lib/isolate/base.dart
+++ b/lib/isolate/base.dart
@@ -65,7 +65,7 @@ abstract class SendPort implements Hashable {
    * running in the same process (e.g. isolates created via [spawnFunction]), it
    * is also possible to send object instances (which would be copied in the
    * process). This is currently only supported by the dartvm.  For now, the
-   * frog compiler only supports the restricted messages described above.
+   * dart2js compiler only supports the restricted messages described above.
    *
    * Deprecation note: it is no longer valid to transmit a [ReceivePort] in a
    * message. Previously they were translated to the corresponding send port
@@ -136,7 +136,7 @@ interface ReceivePort default _ReceivePortFactory {
 
 }
 
-// TODO(kasperl): Make this hashable and document it.
+// TODO(kasperl): Document this.
 abstract class SendPortSync {
 
   callSync(var message);
diff --git a/pkg/unittest/unittest.dart b/pkg/unittest/unittest.dart
index f0cf997102d..528555eca16 100644
--- a/pkg/unittest/unittest.dart
+++ b/pkg/unittest/unittest.dart
@@ -298,10 +298,6 @@ class _Sentinel {
   const _Sentinel();
 }
 
-// TODO(sigmund): make a singleton const field when frog supports passing those
-// as default values to named arguments.
-const _sentinel = const _Sentinel();
-
 /** Simulates spread arguments using named arguments. */
 // TODO(sigmund): remove this class and simply use a closure with named
 // arguments (if still applicable).
@@ -313,6 +309,7 @@ class _SpreadArgsHelper {
   TestCase _testCase;
   Function _shouldCallBack;
   Function _isDone;
+  static const _sentinel = const _Sentinel();
 
   _init(Function callback, Function shouldCallBack, Function isDone,
        [expectedCalls = 0]) {