The Amazing World of Gumball (2011)

S5E20 The Catfish

Gumball and Darwin discover that Grandpa Louie is lonely, so they invent a fictional friend named Muriel for him. However, when Granny Jojo learns that Louie has been chatting online with a woman, she doesn't care that Muriel isn't real—she's determined to protect her husband, putting their ruse at risk.