That is to say: it's a eukaryote (see the membrane-bound organelles?) plucking away at a ukelele while perched atop a cucumber.
Some great geeky wordplay from It's Okay To Be Smart's Joe Hanson, who says the GIF above is "Part 1 of a series... in which I make animations from funny biology rhymes that pop in my head." NB: Hanson says that, to be honest, said series may start and end with the animation seen here. Hard to blame him. We'd imagine it's pretty tough to top a euk with a uke on a cuc.