Castle Smurfenstein is a Smurf-themed total conversion by Dead Smurf Software, of Silas Warner's Apple II game Castle Wolfenstein, published by Muse Software. It is the first ever game "mod".
Homer Simpson makes a reference to this game in the "Medal Of Homer" level of The Simpsons Game.
This is the second and the last Smurfs game published by Dead Smurf Software, with the first being "Dino Smurf", a game which is based on the 1983 computer game Dino Eggs by Micro Fun.
In the game, the Smurfs were created by the Germans which were used to destroy the enemy countries after their failure in World War II. The player would control a person called Smurfbutcher Bob, who was captured by the Smurfs and taken back to their headquarters, Castle Smurfenstein, which was located in Ontario. The player needed to control Smurfbutcher Bob to defeat as many Smurfs as he can and escape, also to steal the Smurfs' plans to stop the Smurfs and the Germans from making their evil plans come true.