Heard once at Ronaldsway -
A commercial aircraft came on frequency, callsign [Company]123, with a pilot obviously known to the controller. The controller then used the callsign [Jim]123 in future exchanges. Shortly afterwards, another commercial comes on frequency, hears the other exchanges and demands to be called [Bob]234. Controller responds, "negative, but you can be Heidi234 if you like." The second pilot declined.