Ah. Yes. The soaking up of reflected glory. Sponge is rather a perfect metaphor for this. This is something we often see in assistants who enjoy the reflective power of their positions. You see it in all those Insider Hollywood stories. (Episodes, The Player, Entourage, The Comeback) There’s always that assistant who disappears into their boss – one who does his dirty work for him, who approves as s/he think he would approve or dismiss where s/he thinks he would dismiss. They can even look alike as the assistant, the sponge starts to soak up so much that his/her natural look is obscured by what it has absorbed.