Happy St. Patrick's Day from all of us on Team Typo. Leprecaun is a bonus word because it has not yet been added to the Main List of Typographical Errors in Library Databases at http://faculty.quinnipiac.edu/libraries/tballard/typoscomplete.html .
On a check this morning, there were three instances of the word in OhioLINK. All three records involved audiovisual works. This is not terribly surprising. The Library of Congress does not, apparently, catalog audio-visuals, so these records are usually added by member libraries of OCLC. Most libraries do not have the levels of quality control found in the Library of Congress, so we expect more trouble. On the whole, this is not a widespread error - in Google, the count of Leprecauns is less than 1 per cent of the count for the correct word. As always, we suggest that you check each record before making a correction.