The kids are invited to a Halloween party at Grandma Griff's house. Later, Stanley, his friends and Dennis then look into The Great Big Book of Everything to learn about bats.
Where to Watch Grandma Griff's Mystery Guest
Cast of Grandma Griff's Mystery Guest
Jessica D. StoneStanley Griff (voice)
Charles ShaughnessyDennis (voice)
Rene MujicaHarry (voice)
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