Waking Nightmare (S07E11)

When Mandy spots Billy entertaining himself with Grim's enormous dog, Cerberus, she urges Grim to keep a close watch on him, as she needs a restful night to prepare for an important test the next day. Motivated by his father, Billy attempts to disturb Mandy's sleep, hoping to sabotage her success and outshine her for once. After a restless night of guarding Mandy's home, Grim is unable to prevent Billy from waking her. However, it turns out that the Mandy he disturbed was actually Irwin, posing as her while the real Mandy snuggled in her dog’s house. Ultimately, Mandy aces her test, leaving Grim facing consequences for his failure to protect her.