A commercial for "Phineas and Ferb: Spot the Diff" that was shown on The Disney Channel during July and August 2008. Unfortunately, the Spot the Diff section is no long available on Disney's website. When it was there, after you completed the quiz you could watch "Does This Duckbill Make Me Look Fat?" (the "never before seen episode"). Disney has also removed that video from their website since it was broadcast on August 10, 2008.
This commercial belongs to Disney, but I'm hoping that they will allow it to remain here as a way of preserving some of the history of Phineas and Ferb.