Pranks are always tough, these aren't getting vindictive are they? If they are out to have fun, try photoshopping him into riske photos, tape/superglue his cubi

Pranks are always tough, these aren't getting vindictive are they? If they are out to have fun, try photoshopping him into riske photos, tape/superglue his cubicle/something down, prank call him (impersonate some offical)...do something that gets his blood running that isn't permanent.