Damn you, internet!
Why must you continue to mock me with your continuous stream of people far more talented than me?!
These amazing origami models are the work of Won Park using dollar bills and are all created within the proper origami rules (no cuts or glue). Manipulating the imagery printed on the dollar in order to create the features of the animals must have taken a frankly ridiculous amount of time and patience.
Link lazily stolen from the excellent Drawn illustration blog.