Much like the cliff swallows returning to Capistrano, Colin Mochrie and Brad Sherwood’s annual improvisational comedy roadshow migrates to the Lehigh Valley and the State Theatre Center for the Arts, Easton, for the “Scared Scriptless” tour, 8 p.m. Nov. 18.

Year after year, flocks of comedy fans journey to the State Theatre to enjoy an evening of laughs and interactive performance as only the two beloved “Whose Line is it Anyway” veterans can deliver.

It is said that If you have seen something once, you have seen it twice. That adage does not hold true for a Mochrie and Sherwood show. The spontaneous nature of their improv comedy makes each performance unique and keeps fans returning.

“We are always trying to come up with new games, especially for the towns [like Easton] we visit over and over again. We have a certain amount of games we do play every time, but they are always different,” says Mochrie during a recent phone call from his home in Toronto, Canada.

“We usually look over the running order that we’ve done over the last couple of years and try to come up with new things.”

Audiences seeking a break from the daily barrage of political commentary will find a welcome refuge for the duration of the show.

“At the top of the show we say, ‘For the next two hours this is a political-free zone.’ We found when we do take political stuff it really divides the audience,” explains Mochrie.

“There are just so many great political satirists out there who can do the job and get their points across. Our show is just goofy fun and we just try to keep it goofy without getting too much into anything political.

“It just makes it more fun for us if that [politics] is sort of taken off the table.”

The silliness abounds when Mochrie and Sherwood take the stage. A loose premise paired with audience suggestions guides the direction of the performance. The ability to “read” your improv partner and to know when to give and take during play are essential for a successful performance. Mochrie and Sherwood combine comedic chemistry and a lengthy history working with one another.

“It certainly helps that we’ve worked together [for so long]. This is our 15th year doing this tour and I’ve known Brad for almost 30 years now,” Mochrie says when asked how the pair keep the show from getting stale over the years.

Although the performers on stage are essential to the show, audience participation plays a key role in Mochrie and Sherwood’s act. Creativity is appreciated, so leave the obvious choices at home. Mochrie says certain suggestions will be roundly ignored.

“Most of the work we do on the show is trying to keep it [the show] to suggestions we’ve never had before. We may ask the audience for an ‘occupation your great grandfather may have had’ or ‘What is your best friend’s hobby,’” explains Mochrie.

“That way we tend to get more things that we’ve never gotten before and that’s kind of the key to keeping it fresh for us and when we get something we’ve never heard of it kind of inspires us.

“Try to think a little outside the box when we ask for suggestions,” Mochrie advises audiences. “So often we get gynecologist and proctologist when we ask for occupations and we’re never going to use that.

“So, make it interesting for you [the audience], and [also] make it interesting for us.”

Aside from the tour with Sherwood, Mochrie has several theater performances scheduled in his native Canada including perhaps most appropriately portraying the fool in Shakespeare’s “King Lear” later this year.

“My wife [fellow comedian Debra McGrath] and I filmed a new TV show in Halifax starring Jane Seymour. There’s always little things that pop up out of nowhere that are always fun and keep the career from going stale,” Mochrie explains when asked about other projects aside from the tour with Sherwood.

“It’s a new half-hour called, ‘Let’s get physical,’” Mochrie says about the show. “It’s about an aerobics instructor and they sort of do ‘80s aerobics competitions. In the show, my wife and I are the judges, almost like Fred Willard in [the mockumentary] ‘Best of Show.’ We’re commentators.”

The show has filmed one episode thus far which will air on PopTV, a CBS property, airing on cable and satellite television.

“It was a lot of fun,” Mochrie says about filming the episode, “[It is] a really nice cast, Matt Jones, who played Badger in ‘Breaking Bad,’ is one of the other stars. It was a really great company to work with.”

As for future episodes, Mochrie is optimistic regarding the future of the show and hopes it will be well-received by television viewers.

Mochrie would like the State Theatre audience to be aware that they play a crucial role in the show.

“They are sort of the other member of our troupe,” Mochrie says of the audience.

“We depend on them for all of our inspiration so if they can think outside of the box when we ask for suggestions, so [please] make it interesting.”

Tickets: State Theatre Center for the Arts box office, 453 Northampton St., Easton; statetheatre.org; 1-800-999-7828; 610-252-3132