the term was invented by
Bart Simpson in the Episode "She of Little Faith" (Episode 275 - DABF02, Season 13) when homer was buliding a model rocket, Milhouse commented that he never knew that Homer was so
interested in Science, but since Homer hates science (and nerds), Bart said Milhouse actually said "pie pants"... to which homer replied "mmmmm pie pants".... later he says "the word un-blowuppable is thrown around alot these days..." freaking
hilarious!