as with the old live action turtles movie it might be because the rat's head was supposed to fit a human facade and they maybe wanted to give the actor at least minimum eyesight... the design was still off the real image of a rat by far. in the Mrs Brisby movie they at leats reid to make them look like rats and mice and a shrew.
the rest... might come from a lack of interest paired with laziness? also many times mustelids of all kinds and hyenas get wolf heads by artists. if they're lucky the artist gives them a cat nose instead. :P

kangaroo faces are interesting. a mix of many distinct shapes from wolf to genet to horse or deer... they deserve a little research for authentic details.

It's why I said *majority* and not all ratties lol. I loved the NIMH movie (they even had male rats as...er...male, in the origin flashback). But no. Rat's don't have wet black noses /at all/ much less shaggy. I know, I used to snuggle with ratties daily (they LOVE to snuggle btw). I guess with rats in general, my main complaint is that they don't live long. I still miss my boys to this day, and made it my duty to NEVER portray them as the typical accepted unkempt werewolf face with bucked teeth design, or evil.

Ha ha mustelids and hyenas always seem to have been drawn with wolf heads- even I've made this mistake. Which is funny, because I had pet ferrets before- their head is anything BUT wolf like. Even their pupils aren't rounded /at all/, but horizontal slits. Their noses are cold and wet like a doggy. Fun fact, you can catch your pet ferret's cold. Had a interesting time exchanging colds between me and my ferret boys of yore.

it's interesting that in a fandom that's so centered about animals many people who go creative don't give damns...

hell, there are even differences between wolf and fox,and they don't catch it. XD

I'm SO GUILTY AS CHARGED
Though I had my reason in the fox/wolf case-
Largely because its (Keith for example) not a 'fox' as in a Earth fox, but a alien race of tall canid-type race known as the 'Vulpecula'; a dynasty of beastly, egomaniacs, that despise being called 'dogs'. 'Refined werewolves' in royal clothing, is what I had a character describe them as appearing. The wolfish look was intentional.

BUT if its not intentional, I can't defend that one aside from being someone's art style... Personally, I try to keep foxes small, with less pronounced obvious wolfish features.
I stress TRY. Did I mention TRY? I TRIED, I mean TRY LOL!!!! Oh BOO, I like big jagged toothy grins

aliens are different. they look like wolf at first, but there are differences, because they are NOT terranean wolves... they are aliens looking like ones. :) so you're excused.

besides, I try myself. hard as a rock.

Too true. XD Does make for fun 'mistaken identity' type shenanigans though!

Splinter always looked like a wolf until the most recent and 2k3 version