As you may recall, FOX advertised this as the “300th episode,” and even included a “300th episode” banner in the opening sequence (seen in syndication also). I think FOX just wanted to include big stars like Blink-182 and Tony Hawk in their landmark episode (like they used Steve Martin and U2 in their 200th and The Who in their 250th); there were none in the “real” 300th episode, unless you count Pamela Reed as Ruth Powers.