The Bad News Ghouls/House of No Tomorrow

Plot:

In "The Bad News Ghouls", when Billy's baseball team (that is playing against Mindy's own team) turns down Mandy as a new teammate because she is a girl, she has Grim disguise her as a boy named Manfred. In "The House of No Tomorrow", Billy, Mandy and Grim's outing to a character-themed amusement park goes south when they stumble upon and enter the abandoned House of Tomorrow.