"Almost" is a bit vague and probably too strong, but they are mostly water, just like other mammals.

Therefore they are more properly classified as soups.

Noted ontologist Pirate Software would argue that cats are a Wellington, not a soup.

https://youtube.com/shorts/MnAegCmJ7Xk

I can't refute his logic.

Save for their skeletons and other dry structures like hair and shells, animals are in fact gels.

Maybe they're more broth-like? Also the paper at https://www.drgoulu.com/wp-content/uploads/2017/09/Rheology-... seems to indicate that they are "active rheological materials" and therefore probably non-Newtonian.

Catchy headline, but also in a fluid in a dynamical sense - cats "flow" into spaces when exploring by trial-and-error testing openings with their body size, but they are also only "almost" liquid in that for especially narrow openings they are reluctant to poke their heads in, presumably because they might get stuck.

The contrast with dogs in the introduction is instructive: dogs tend to hunt over open fields rather than chasing prey into narrow dens, so it makes sense they would tend to make conservative eyeball judgments about whether they can fit into certain spaces. But cats will try to corner their prey in a tunnel/etc, so they have good reason to rely more on touch and experimentation ("ecologically-valid strategy").