William Shatner

For his role as Shawn Spencer on Psych, James Roday has had to do a lot of crazy things over the years (see: dressing up like a vampire, engaging in a kung-fu battle). But the craziest may have been asking guest star William Shatner to appear in a Psych video for Comic-Con earlier this year.

"I was so nervous asking him to do that. It all ended up in my lap and everybody was just sort of crossing their fingers, like 'Roday, go see if you can get him to do this,'" the actors tells TVGuide.com. "And he was just so accommodating and so lovely. I think he could tell I was nervous about asking him and he totally put me at ease. He was like 'Of course, I'll do it.'"

Exclusive sneak peek: William Shatner cashes in on Psych

Getting Shatner to star in the video — in which he told "Psych-Os" everywhere to keep up the good work — was just the first step of his initiation into the Psych universe. On Wednesday's episode, airing at 10/9c on USA, the Star Trek vet will play the con man dad of Juliet (Maggie Lawson). "Psych kind of lives in tribute of pop culture and it doesn't get much bigger than William Shatner. But I think the key for us was don't use him as a joke, don't use him as a gag," Roday says. "Acknowledge the fact that he's William Shatner, but give him a great role with good stuff to do because he's also a tremendous actor."

Shatner's character, Frank, returns to Juliet's life just in time for her birthday but nobody can tell whether he's really kissed his life of crime goodbye or whether it's just an act to win back his daughter. To make matters worse, Shawn stops at nothing to win over his girlfriend's dad even though she wants nothing to do with him. Roday made sure it was a part worth Shatner's time. "He's an 80-year-old who has as much, if not more, energy than Dulé [Hill]. and I. He had probably the heaviest load any guest star on our show has ever carried," Roday says. "He was working all seven days all day, and then the one weekend we had off, he did two live shows. He's unstoppable."

Psych's James Roday on Shawn and Juliet, Gus' growing pains and breaking all the rules

Although Psych has welcomed plenty of big name guest stars over the years — including this season Molly Ringwald, Danny Glover and Jason Priestley — Roday remembers a special feeling in the air the week of Shatner's episode. "We were all just kind of in awe. It was also the first time that you could tell that our show's crew was collectively star struck," Roday says. "We get a lot of great people, but everybody kind of showed up with their merchandise, hoping to get an autograph or get a picture."

Watch a sneak peek from Wednesday's episode: