It's Always Sunny in Philadelphia: Season 3, Episode 3

3 - 3: Dennis and Dee's Mom is Dead

Dennis and Dee's abrasive mother has died, and the bad news is that she stiffed them in her will, leaving all her money to her humanitarian paramour, Bruce Mathis (Stephen Collins). But at least Dennis got her house. It's a "party mansion," and that's how he intends to use it.