Curious George (2006)

S2E11 All-New Hundley

George feels frustrated with Hundley, who refuses to let him enjoy the lobby, wishing instead that his pet would share his playful spirit. One day, he observes Hundley barking energetically and exhibiting a lively demeanor, exactly what George had hoped for. However, he soon realizes that Hundley is alternating between this spirited behavior and his usual calm self. Concerned about Hundley's sudden shift in personality, George embarks on a quest to uncover the truth behind this peculiar transformation.