Canaan is singing "Wheels on the Bus". He was singing away, then he got to "The bunnies on the bus go..................." (long silence).
Abrupt switch-"The horn on the bus goes toot toot toot!" Apparently, there is no noise acceptable for bunnies to make.
After the horn, he moved on to moose-"The moose on the bus go moose moose moose!" I guess moose noises are hard to pin down too.