J. G. Quintel
The blue jay
No
Mordecai from the Regular show? He was voiced by the creator
J. G. Quintel
If the Mordecai you are referring to is the one from Regular Show, than the voice actor is J.G. Quintel, the show's creator.
Mordecai , is voiced by the show's creator J. G. Quintel .
Pops Maellard is voiced by Sam Marin .
Sam Marin provides the voice for the Muscle Man character on the Regular Show series. He also does the voice for Bension and Pops in this series as well as few characters in the Adventure Time series.
Mordecai Jones was born in 1813.
No one
Dan Povenmire, one of the original creators of the show. Of course, that's not his regular voice.
Nope, his early recordings (i.e. Closing Time, his debut, to around The Heart of Saturday Night and maybe later) show that he had a very regular voice. Excessive smoking may have caused his voice to change.