update: The silhouette now has a page in Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Hughmann_for_scale.svg
SpaceX has a history of using dummies/models/mannequins on the test vehicles.
Grasshopper, the Falcon 9 landing test vehicle had a cowboy mannequin strapped on for test flights. But the bulked up landing legs, had room to mount a dummie. Starhopper less so, and has a more powerful engine (when running with 1 and 3 are coming).
The Tesla Roadster launched on the first Falcon Heavy flight had a mannequin in a spacesuit (Starman) in the drivers seat.
(Cheese wheel on the first Dragon as a further joke, etc).
This is just a continuation of the man in the loop testing they have been doing.