"Master of Fail Disguises" is SMG4's 16th Blooper.
Mario is seen jumping out from the pit that leads to Bowser's arena holding a key. He also mentions that with the key he can go to a lot of places including the castle's kitchen and Peach's Bedroom. He then looks for his gun. Toad then reminds him that the next day was Peach's birthday. Mario then plans to give Peach a butterfly. The butterfly then starts to fly away and Mario chases it, making a mess in the castle. The butterfly had supposedly grabbed Mario's gun and punched him. Mario then kills the butterfly. Peach hears the commotion and goes inside. Mario then blames it on Toad. Peach then says that Mario and Toad aren't allowed to go to her party.
The next day, Mario watches the news about Peach's birthday. Mario then talks to the castle guards. Mario then uses multiple disguises to try to get inside.
When he got inside, using his "secret" way, Mario finds out that the party was over. He then finds Peach outside and apologizes. Peach forgives him and asks for a present. Mario then brings Lakitu and throws him to the castle. Peach then walks into the ground and the video ends.