Special Delivery 64 is a ROM hack created by Big_Boss and Subspet for the SimpleFlips' Slide Hack Competition (2024) ft. PirateSoftware.
Some custom mechanics have been used to alter the gameplay. Among them is the checkpoint system that takes effect whenever the player dies. Coins also no longer heal Mario, making dying to any of the custom electrified objects far more likely.
In this hack, Mario is employed by a delivery company called Uppies, and has been called in to make an urgent delivery to Peach's Castle. His boss informs him that he won't be receiving pay for this job but has to do it regardless, or else they will fire him. The warehouse containing the delivery is also locked as it is outside the company's typical working hours, so Mario will need to find a way around that.
The first challenge requires Mario to find a way into the warehouse. This is done by wallkicking up the side of the building and entering the chimney. Once in there, Mario will need to complete a slide gauntlet in order to reach the delivery, which definitely isn't a retextured Power Star. He will then be taken to the next level, which is also a slide gauntlet, but takes place outside and has a few different routes available. In the entire section, the snow is actually quicksand that will instantly kill Mario. All of the diverging paths lead to the same ending, but with a small handful of variations on the path and its obstacles.
Upon reaching Peach's Castle at the bottom of the slide, Mario will need to run over to the lorries/trucks on the left in order to stop the timer. There seems to be no penalties or rewards for times finished, nor for coin count. Talking to the Toad who receives the delivery will reveal that the urgent delivery was actually for a game called Special Delivery 64, that Toad couldn't wait to play.