"It seemed like a cool idea at the time," the Star Trek star tells PEOPLE

William Shatner felt the heat Sunday at a Comedy Central roast in his honor.

The Star Trek and Boston Legal star, 75, arrived at the event, filmed at the CBS Radford Studios in Studio City, Calif., and slated to air on Comedy Central on Aug. 20, riding a horse – and thereafter was referred to as an ass.

Asked why he would subject himself to such insults, Shatner told PEOPLE earlier, “It seemed like a cool idea at the time. No one can say anything that hasn’t been said already.”

In a videotaped plea, Shatner’s Miss Congeniality costar Sandra Bullock asked the roasters to “go easy on the old coot,” but that didn’t stop Shatner’s Star Trek costars, roastmaster Jason Alexander and comedians including Andy Dick and Greg Giraldo from slamming everything from Shatner’s paunch to his hair to his hammy acting style.

As Shatner sat in Captain Kirk’s chair from the original Star Trek, Farrah Fawcett took a stab at his “so-called singing career” before introducing clips of Shatner’s musical efforts through the years.

Andy Dick wore pointy ears and a blue uniform to reveal that he is the secret love child of Captain Kirk and Mr. Spock.

Star Trek’s Lt. Uhura, Nichelle Nichols – who first worked with Shatner when the series debuted 40 years ago – told PEOPLE on the red carpet, “Bill always gets what he wants. Tonight we get what we want. It’s payback time.”

But Shatner may still get the last laugh: On Emmy night, Aug. 27, he’ll vie for best supporting actor in a drama for his portrayal on Boston Legal of eccentric lawyer Denny Crane – a role that has already won him two Emmys.