The problem with MyHouse.wad is that it doesn't work with custom class mods due to the fact it changes a number of stuff with the gameplay or weapons.
I don't know, he must have modded MyHouse.wad in order to make it work with Peppino or he extracted Peppino into its own mini-mod. Either way I don't know.
Wait, he's using a far older version of BYOC (aka one of the Betas) which somehow does work with MyHouse.wad.
Skill issue.