Certain bodies

Certain bodies can pass through solid walls painted to resemble tunnel entrances; others cannot.

This trompe loeil inconsistency has baffled generations, but at least it is known that whoever paints an entrance on a walls surface to trick an opponent will be unable to pursue him into this theoretical space. The painter is flattened against the wall when he attempts to follow into the painting. This is ultimately a problem of art, not of science.