The "Homological cohomology memes" facebook page recently posted an image, copied below.
In the 4th panel, there are maps from $c$ into $\mathbb{R}$, from $\ell_\infty$ into $\mathbb{R}$, $f: \mathbb{R} \to \mathbb{R}$, and $A_f: c \to \ell_\infty$. What are these maps?
Panel 1: $\epsilon$-$\delta$ continuity
Panel 2: sequential continuity
Panel 3: topological continuity
Panel 4: ???
Panel 5: continuous functor