These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fridge Brilliance: In "Flying", Mr. Grumpy says that he started working as a flight attendant 30 years ago. 30 years before the episode premiered was 1978, when Mr. Grumpy's book was released.
Hilarious in Hindsight: When the show first came out, various fans of both this and Thomas & Friends did parody clips depicting several Thomas characters as the Mr. Men and Little Misses. A year later, some of the UK voices from the show would play characters for Thomas.
Memetic Molester: Mr. Tickle comes as close as a character can for a lighthearted kids' show.
Seasonal Rot: The second season could be considered weaker than the first.
Squick: Mr. Messy has some rather revolting habits, especially to a Neat Freak like Mr. Persnickety/Fussy.
They Wasted a Perfectly Good Character: Mr. Tall and Little Miss Curious. For most of Season 2, they were relegated to nothing more than cameos, and even their speaking appearances had little to no bearing on the plots of the sketches they appeared in. Mr. Tall would've had great plots concerning his height, and Little Miss Curious could start one off with a question. Alas, it was not to be.
Toy Ship: Despite the series aimed for young children, at one point, it seems, during Season 2, that the writers and animators were teasing of hints of Mr. Grumpy with Miss Chatterbox for some odd reason.
The Woobie: Mr Bump. He has Miss Whoops for a sister. I'd hate to be him. And in some cases, this trope can expand to Mr Quiet. Miss Calamity, until her disappearance in season 2, was also part of this trope.
However, since some people are amused by how Mr. Bump gets repeatedly harmed, you could describe him as The Chew Toy. Miss Calamity fitted this trope, too.
Mr. Happy is also considered one. There are some fans who feel sorry for him. While the Chew Toys/Butt Monkeys always express how they feel and get back on their feet, Mr. Happy has to hide his other emotions behind a smile and suffer in silence.
Mr. Nervous. He's practically scared of life itself!
Mr. Quiet - the poor dude is just looking for some peace and quiet but ends up being walked over by others or dragged into their mess.
Miss Sunshine in the Surprise skit (even if it was for a moment).