HatchEgg
HatchEgg command
Contrary to its name, this does not hatch the egg you are aiming at; it only resets its incubation progress to 0%, so the right temperature is still required to hatch it. With unsuitable temperature the egg shows the broken icon and cannot be eaten afterward.
Using cheats on a server
On a multiplayer server, authenticate first with enablecheats <password>, and prefix admin commands with admincheat instead of cheat.