A stamp is a collectible found in the game Super Mario 3D World that Dashie used to play for the Dashiegames channel.
Stamp are found in every level of the game, and Dashie considers them worthless, as they are difficult to collect and only serve the purpose of a drawing of a character from the game to look at, and are not required to beat Bowser. However, it is revealed the player is required to collect every single stamp to unlock the final level. Dashie's attitude towards them still does not change, however. A fan collected all the Stars and Stamps in the game and sent the save file and console for Dashie to try out. However, after trying to complete the level, a reaction video and one more last video with him trying out old difficult levels, he technically finished the series, while still occasionally coming back to it.