Sometimes, when it is time to clean up, I say, "Mona" and students then reply by saying, "Lisa". I learned this attention grabbing strategy from a few fellow art teachers on Pinterest. The idea is that students should reply by saying, "Lisa", while posing like this famous portrait. They should have their arms folded, mouths closed, and eyes on the speaker.
Instead of saying Mona, I shared this video with my students. They thought it was a fun twist to see Mona come to life and assist us with preparing to clean up.