A wonderful bird is the pelican
His mouth can hold more than his belly can
He can store in his beak
Enough food for a week
I'll be darned if I know how the hell he can.

Ogden Nash, I think. And then there's one I wrote for my fellow civil war re-enactors. We have one guy in our group, a high-school kid, who portrays a rather dandified young man and hauls an amazing amount of crap to each event. Thus:

There was a young dandy named Joe
Whose pile of possessions did grow
His portable house
Lacked only a spouse
And made packing exceedingly slow.

And one more Kimmers original:

There once was a fellow named Kevin
Whose mustache did grow up to heaven
He combed it out daily
With his ukulele
Each day at a quarter to seven.