A (usually) non-serious phrase that can be said by a person in reference to something they just witnessed or were told about that's often, but not always, very difficult or nearly impossible to do in real life.
Humorous and fallible attempt to try and milk coolness/points from any form of audience.
Wizard: *shoots lightning bolts out of his ass*
Steve: I can do that but I don't wanna.
Person in commercial: *jumps out of a plane while doing his taxes and fighting off a lion*
Jimbo to Molly: I can do that but I don't wanna.
Lance: Man, I just saw this sick stunt. The guy was handcuffed while riding a motorcycle down a ramp, and then jumped through 5 fiery hoops over a shark-infested pool that also had spikes at the bottom of it.