Fraggle Rock (1983)

Season 3: Episode 2

Red absolutely loves her radish bars (which are the equivalent of Pop-Tarts in our world). So when she sees that whenever she wakes up from sleeping that her bars are missing, she sets out to find the crook, which leads her to think her roommate Mokey stole them. She also gets Gobo to hide in a hole outside her room to watch and see if it really is Mokey; after Gobo gets distracted from reading a postcard, the bars go missing again, but Gobo claims he didn't see anything. So finally she gets Wembley to stay the night with her to catch the thief, and what Wembley finds ends up being quite surprising.