The Clerihew is a form of comic verse invented by Edmund Clerihew Bentley, and championed by his friend, the novelist Gilbert Keith Chesterton. It consists of four lines of irregular length, rhymed AABB, or two uneven couplets, if you prefer to think of it that way.

Clerihews are almost always biographical, and the first line usually consists solely of the subject's name, perhaps the most famous example being:

    Sir Christopher Wren
    Said, "I am going to dine with some men.
    If anyone calls,
    Say I am designing St Paul's."
    (Bentley)

They may also be about a non-human subject:

    The art of Biography
    Is different from Geography,
    Geography is about maps,
    But Biography is about chaps.
    (Bentley)
  
Or, indeed, about a fictional character:

    B. A. Baracus,
    Slightly crackers
    How the heck did you survive Saigon?
    You dress more conspicuously than Elton John
   (Tim Clare)

Or a frivolous fiction about a fictional character:

The marine from Halo
    got engaged to J-Lo.
    She said, "He's a real armful,
    you know? But he's got a cute arsenal."
   (Me)

Recommended reading:

The First Clerihews by E. C. Bentley, illustrated by G. K. Chesterton