Synonyms for Monkey (same or very similar meaning)
WordNet sense 1 (one who is playfully mischievous):
imp, rapscallion, rascal, scalawag, scamp, scallywagWordNet sense 2 (play around with or alter or falsify, usually secretively or dishonestly):
fiddle, tamperWordNet sense 3 (do random, unplanned work or activities or spend time idly):
potter, putter, tinker, mess around, monkey around, muck about, muck aroundFrom the ODE community, based on WordNetadd/edit