In Dry Dry Desert, north of Kolorado's camp you can find a yellow block which when hit multiple times will reveal three hidden '?' blocks which subsequently give you a Shroom (1 hit), Super Shroom (10 hits) and Ultra Shroom (100 times). This block keeps track of how many times you hit it and has a maximum unsigned four byte value of 4,294,967,295, which means that hitting it more than that amount would reset the blocks and spawn them over the existing ones allowing you to get the Shrooms again, which would take 36.29392 years to reach. Hitting the block another 4,294,967,295 times would reset it again, causing the hidden blocks to spawn over the existing ones again. Continuously repeating the process until the game freezes would take just over 416 years to achieve.