In his review of Doug, the Critic mistakes the characters for being in High School. It is clearly stated in at least one episode that Doug is eleven-and-a-half years old, and in the final episode, it is stated that he is going into junior high school.
The Critic refers to Heffer as a cow; he's actually a steer.
When reviewing Rugrats, the Critic refers to Angelica as Angela at one point.