Yally is a student and a friend of Little Monster from Little Monster at School. He is depicted as a bulldog-like monster (resembling a bull dog like Binky Barnes from Arthur and the three Arthur Living Books games Arthur's Teacher Trouble, Arthur's Birthday, and Arthur's Reading Race). He is grumpy when he doesn't get his way. Yally is frustrated with school when he makes a mistake with spelling letters. He is mad when he doesn't get to be the best counter, doesn't know how to water plants, and doesn't like being near pets. At lunch, when lunchtime is outside, he also nearly gets sick from eating too much junk food at lunch. Little Monster narrates that while he brings the same thing for lunch (a sandwich and a tango), Yally brings lots of sweets. Grendella says to Yally, "YALLY!? YOU SHOULDN'T EAT SO MUCH CANDY!". When the next page is clicked on, when Little Monster (who tries to get Yally to bring healthy food for lunch instead of lots of candy) asks Yally if he wants half of his sandwich, he says, "No thanks". He states he doesn't want to because he doesn't feel so well. At lunch recess, he doesn't like playing games.
He likes telling stories of how he hit the Giant Pirate on the finger and poked him on the nose (with a sword). He is disappointed when the class doesn't read his favorite book about horrible people from outer space (even though Little Monster chose Little Monster and the Three People). The final straw comes when Yally does not get to choose a story (even though he wants a story about people from outer space). Little Laff suggests to him that he can choose a story he likes next time. (That is, as he --Little Laff-- says, "It's OK, Yally. We can always read a story you like next time".) Yally (when clicked on --and response to that) mutters angrily. (That is, but half bitterly crying.) However, near the end of the day Yally is happy when he draws his picture and shares it with Little Monster who he makes a friend with.