|Intro||The Flintstones: The Rescue of Dino & Hoppy - Title Theme & Ending|
|Type||Hit and Run Chaser|
|Signs of nearing||Sounds from the Bootleg game, 7 Grand Dad|
|Origin||GRAND DAD: Super Mario 7|
|Theme song||NPC - Title Theme (The Flintstones: The Rescue of Dino and Hoppy Remix)|
Grand Dad is a boss in Slender Fortress.
Grand Dad is one of the split personalities of Fortran. He comes from Super Mario 7: Grand Dad. He can be possible brothers with Ivortran and considered Weegee's and Malleo's half uncle. He is technically Fortran due to him and Ivortran being created when Fortran riched too much and split into two.
He's a very very nice meme that came from Joel and has recently been elected president of the bootlegs. He has nice feet.
In Slender FortressEdit
Grand Dad function like Jason Voorhees (because of Grand Dad The 13th). His animations is just the same as N64 Mario does. He is just like other hit and run bosses, spawns behind the players, giving no mercy to the sprint or the players, and somehow this boss and Jason Voorhees is the easiest bosses on hit and run types that instant kills on hit, Grand Dad has a method to catch a person, first he will target a person to chase, after the chase for a few seconds, if the area has a very large rooms to fit in and can be spawnable for Grand Dad, Grand Dad will spawn and will chase the player, and will keep doing that until the player is dead or the player found a very crowded place for a hit and run boss not making spawns, Grand Dad appears to be the only hit and run boss that is very persistent than others, chasing some peoples for over 10 seconds.
- Grand Dad had made his oss pack called "Grand Pack" where he, SiIvaGunner, and other Grand-skinned bosses appeared on this pack such as Shrek Dad (plz mashup the All Star song with The Flintstones theme song), Slam Dad (his theme) and other Slender Fortress bosses who are reskinned as Grand Dad as well.