Bertha is a female bus driver who drives buses for Third Street School. She has appeared in multiple episodes, even being part of the main storyline on one occasion.
She drives a yellow school bus that she has nicknamed "Old Smokey", which is seen taking the children on a field trip in "Operation Field Trip". In the episode, the school bus breaks down on a count of it being really old and used which upsets Bertha greatly. The kids, led by Gretchen and Spinelli, use parts that are laying around to fix the broken-down bus which is seen to be working better than ever.