Grotesque
Tenniel's "grotesque" was one reason why Lewis Carroll wanted Tenniel as his illustrator for the Alice books, in the sense of imparting a disturbing sense that the real world may have ceased to be reliable. Tenniel's style was characteristically grotesque through his dark, atmospheric compositions of exaggerated fantasy creatures carefully drawn in outline. Often the mechanism was to use animal heads on recognisable human bodies or vice versa, as Grandville had done in the Parisian satirical journal Charivari. In Tenniel's illustrations, the grotesque is found also in mergers of beings and things, deformities in and violence to the human body (e. g. when Alice drinks the potion and grows huge), and a proclivity to deal with ordinary things of this world while presenting such phenomena. The most noticeably grotesque is Tenniel's famous Jabberwock drawing in Alice.
The Alice illustrations combine fantasy and reality. Scholars such as Morris trace Tenniel's stylistic change to the late 1850s trend towards realism. For the grotesque to operate, "it is our world which has to be transformed and not some fantasy realm. The illustrations constantly but subtly remind us of the real world, as do some of Tenniel's scenes derived from a medieval town, the portico of a Georgian town, or the checked jacket on the White Rabbit. Additionally, Tenniel closely follows Carroll's text, so that the reader sees the similitude between the written text and the illustrations. These touches of realism help to convince readers that all these seemingly grotesque inhabitants of Wonderland are simply themselves, simply real, not just performing.
https://en.wikipedia.org/wiki/John_Tenniel#Style