A Grim Day (S06E12)

When Billy heads off to spend time with his grandmother, Mandy takes the opportunity to enjoy a day of relaxation, leaving Grim with some unexpected free time. However, boredom quickly sets in, prompting him to pay a visit to General Skarr. In a twist, Grim lends Skarr his enchanted scythe, which Skarr uses to create an army of enormous lawn gnomes. Missing the usual company of Billy and Mandy on his escapades, Grim recruits Mindy and Pud'n to help reclaim his scythe. Though they initially rise to the challenge, the duo flees in fright when Mandy spots their peculiar gathering.