Stew peters actually has a good vid
(twitter.com)
Its not as much about the shape of them or anything but their placement. They are lower up the skull but combined with their nose they give them this weird appearance of a rat. Depends on their phenotype too of course. They do look weird. The more I started paying attention I realized its not as much about the individual features like oh this one has got a big nose. Once youve seen enough of them you can spot them even from far away.