It's hard to tell when something in the physical world will catch Phalanx's attention or go completely beyond their notice. Often it's the shiny or repeating things that are most of interest--the henges of beer cans as an example--with everything else blending together as one big meaningless backdrop, but the behavior is not always that predictable.

Vincent's bathroom, for example. There shouldn't be anything about this space that is particularly eye-catching, but Phalanx's attention immediately goes exploring, and it's not to the tub or whatever toiletries might be setting out on the counter. For whatever reason, Phalanx apparently finds the walls here fascinating.

Even Robin's question about disrobing isn't enough to distract the creature. Phalanx only murmurs some inarticulate, noncommittal sound in response, and doesn't make a move to begin the whole undressing process.