While it may seem a disappointing revelation to genre fans, director Mike Mendez admits the idea of making a movie about a rampaging giant spider did not initially strike him as a career booster.

A few years back, a screenplay about a eight-legged monster terrorizing Los Angeles came across the director’s desk. Helming a “schlocky B movie” was not that big a stretch for Mendez. His resume includes such titles as Gravedancers, The Convent and Killers. He even received a co-directing credit, although apparently wishes he didn’t, for a 1997 film called Movie Bimbo Bash.

Still, discovering this particular screenplay on his pile was something less than an epiphany.

“It came to me as a script called Dino Spider and I was very sad about that and thought my career was over,” jokes Mendez, on the line from Los Angeles.

Which, he is quick to point out, doesn’t mean the script was terrible. It had a good foundation. The premise was sound. Eventually he saw it as an opportunity to redeem the rampaging-monster genre, which he says had been steadily decreasing in quality over the years.

“My problem with these types of movies is that they have these really outlandish titles that seem like they should be fun, but the movies are just really bad and drug the whole genre down into the mud and people would just dismiss the movie immediately by the title,” Mendez says. “I felt we could do something. There had certainly been a number of giant monster movies that are cool and fun. So I looked at it as an opportunity to do something with it and elevate it a little bit.”

The first step was to fit it with an even more outlandish title. So Dino Spider became Big Ass Spider! The second step was to polish and tinker with the original screenplay. The third was to then throw out the revamped screenplay upon casting stars Greg Grunberg and Lombardo Boyar, who both happen to excel at improv and comic timing.

“We tried to make a set that was really open to ideas and improvisation and hopefully set a stage where the actors could play,” Mendez says. “And it just seemed to work out great. It was a joy to watch. Once it was going you didn’t want to stop them. They were just great.”

So while Big Ass Spider!, which opens the Calgary Underground Film Festival on Monday at the Globe Theatre, certainly doesn’t hide its B-movie leanings, it’s also fun and smart and often quite funny. Grunberg, best known for the TV series Heroes, plays a pudgy and slightly over-confident exterminator who offers his skills to the military after a rapidly growing arachnid escapes from an L.A. hospital and wreaks havoc on the populace. Boyar plays a Latino security guard who assigns himself to Grunberg as official sidekick. Clare Kramer plays an easy-on-the-eyes Lieutenant who becomes an unlikely damsel in distress for the two to rescue. Ray Wise, best known as the unhinged Leland Palmer in Twin Peaks, plays her no-nonsense military boss.

There are plenty of nods to the B-movie genre, including a cameo by the master of schlock himself, Troma Entertainment’s Lloyd Kaufman, and an appearance by cult-favourite actress Lin Shaye.

But the star of Big Ass Spider! is the big-ass spider herself. While the special effects aren’t exactly at Hollywood-blockbuster levels, she is convincing enough to provide more than a few chills in between the laughs. The effects were done by a company in Pakistan, of all places, by artists who were looking for a flagship project to establish themselves in film. Ambitious workers who are willing to offer their services for cheap are a godsend for low-budget filmmakers.

“It was all done via Skype and remotely via the Internet,” Mendez says. “But, other than the hours being really odd, they did a really good job considering it was a tiny, tiny budget.”

Of course, Mendez has a good deal of passion himself for the B-movie underground. His Internet Movie Database entries as an actor include roles such as the Invisible Ninja in 2010’s The Black Box and something called the Corpse F—er in 2011’s Chillerama. But as a director, his filmography also boasts the documentary Masters of Horror, a TV project that allowed him to interview genre heroes such as Wes Craven, Tobe Hooper, George A. Romero and John Carpenter, among others.

There are certainly shades of Kurt Russell’s swaggering hero Jack Burton from Carpenter’s Big Trouble in Little China to be found in Grunberg’s exterminator. In fact, there are plenty of nods to horror-comedy and sci-fi in Big Ass Spider! In its program, The Calgary Underground Film Festival astutely points to the 1990 classic Tremors as a touchstone. But there are also nods to Ghostbusters and Aliens on display. And, of course, any film of this ilk will inevitably be compared to B-Movie master Roger Corman, whose iconic reputation certainly exceeds his output of films that could actually be considered good. Nevertheless, Mendez takes it as a compliment.

“Corman, obviously, is a legend,” he says. “He’s done lots of bad films and some good ones. So hopefully we’re closer to the good ones than bad ones.”