The toy shop employee in "Gotta Fix Squawky", episode 110, is voiced by Roger C. Smith - who is also the voice of Mouse and Moose.
Episode 110, "Gotta Fix Squawky", is the first time we get to see Cat's basement workshop where he most likely creates his many inventions.
Boats and trains both use whistles to communicate. Trains whistle one long signal when they stop, two long signals when they release their brakes and proceed. There is no signal for "bring me a cookie", an obvious oversight.
In "Sick Day", episode 110, we see Pig and Dog's bedrooms for the first time. For all of the bedrooms, much care was put into ensuring that the designs and colors are an accurate reflection of each characters personalities.
In episode 110, "Sick Day" we get to see some of Cat's more interesting inventions.