For three years, German scientists tried to coax a sloth [wiki] into moving up and down a pole for a scientific experiment:

The sloth, named Mats, was remanded to a zoo after consistently refusing to climb up and then back down a pole, as part of an experiment conducted by scientists at the University of Jena's Institute of Systematic Zoology and Evolutionary Biology.

Neither pounds of cucumbers nor plates of homemade spaghetti were appetizing enough to make Mats move.

"Mats obviously wanted absolutely nothing to do with furthering science," said Axel Burchardt, a university spokesman.

The scientists finally gave up and place Mats in a zoo, where is is very comfortable now: Link - via Clive Thompson's Collision Detection