Uncle Albert is a jolly, kind old man who lives in a small home in London. He is the only known relative of Mary Poppins, and appears to have full knowledge of her abilities. He appears to suffer from an unnamed condition, triggered by laughter, where he floats into the air, a condition which Mary describes as "quite serious". Bert reveals that his episodes are fairly common and that it "took three days to get him down" the last time it occurred. Though he loves having company, he becomes terribly sad whenever someone must leave.
Role in the film
While out on errands, Mary Poppins, Jane and Michael learn from Andrew the dog that something has happened to Uncle Albert, though his name is not mentioned at that point. Mary quickly announces a change of plans and heads to his home. Upon reaching the house, she finds that Bert has already arrived.
Upon entering the dining room, the group sees Uncle Albert floating in the air, near the ceiling. Mary reminds him that he had promised not to allow this to happen again. He apologizes but notes that he loves laughing too much. When the children begin laughing, Mary warns them to stop, as the condition is both very serious and very contagious. Meanwhile, Uncle Albert sings about his love for laughter. Halfway through the song, Bert "catches" the "illness" and floats up beside him. The two then finish the song as a duet. As the song ends, Jane and Michael are laughing so hard that they join them in the air.
Uncle Albert and Bert entertain the children by telling various jokes, which send everyone, except for Mary who remains stoic, into hysterics. Eventually, she tells the group that it is time for tea, and she refuses to have her schedule interrupted. Uncle Albert reveals that he has a splendid tea set and ready to serve. She responds that it is getting cold, and he begins to respond with what he had planned. She understands what he is implying before he finishes, and uses her powers to make the table float into the air. She herself then floats up, as she expects that they will want her to serve.
Uncle Albert, Mary, and Bert make conversation, which is constantly interrupted by his jokes. He is so happy that he wishes they could stay. Michael is certain that they will have to, as there is no way back down. Uncle Albert then reveals the cure, somewhat reluctantly, which is to think of something sad. Mary asks him to begin. He starts by telling the story of a man who ran over a woman's cat, and his offer to replace it. As a result, everyone begins to float down. However, the sad story ends with a joke, much to Mary's chagrin. Uncle Albert apologizes, saying that he can't help but have things end funny. After looking at her watch, Mary reveals that they must head home, which is sad enough to have everyone return to the ground. Mary and the children promise to return, but Uncle Albert is now very upset. Bert offers to stay for a bit. Uncle Albert tells them how he always enjoys company but gets very sad when they must leave. Michael tells him that they'll come back soon. Bert attempts to tell a joke to cheer him up, but it fails miserably, and he is left crying. He isn't seen again for the rest of the film.