Danny Trejo is one of Hollywood’s most famous bad guys, but he’s showing off his softer side -- er, sort of -- on this week’s episode of The Flash!

In Tuesday’s all-new ep, titled “Elongated Journey Into Night,” Trejo stars as Breacher, one of the “most feared and dangerous bounty hunters in the multiverse.” Oh yeah, and he’s also Gypsy’s dad.

Breacher comes calling on Earth-1 at a particularly inopportune time for Gypsy (Jessica Camacho) and Cisco (Carlos Valdes) -- and immediately threatens to hunt down and kill his daughter’s boyfriend. But it turns out, the process of getting Trejo to agree to the cameo was much less painful.

“Once the image of it being Danny came into our heads, we sort of couldn’t imagine anybody else doing it,” executive producer Andrew Kreisberg told reporters earlier this week. “I think a lot of times, you don’t ask because you’re afraid, or you just assume people would say no. But you never find out if you don’t ask. We asked, and he said yes, and it’s awesome.”

The CW

RELATED: Danny Trejo Is Coming to 'The Flash,' Michael Emerson Joins 'Arrow' & More CW Superhero Casting News!

For Trejo, the chance to flex his comedic chops -- his “hunting” of Cisco essentially devolves into a hilarious game of hide-and-seek amidst Star Labs’ secret passages and high-tech workspaces -- was a welcome opportunity.

“I love comedy,” he said. “Being fierce ain’t that hard, you know, you just show up.... But I liked the way that they put menacing and funny together, sometimes it would just crack me up… I think that’s what entertainment is, just being able to go from this menacing character to making people laugh.”

The dynamic between Breacher and Cisco is a true highlight of Trejo’s guest appearance, as the two move from hunter and prey to a begrudging -- if still slightly lethal -- respect by episode’s end. The action star said his scenes with Valdes were “a lot of fun,” praising his co-star as “a really great actor.”

The CW

“His timing is awesome, and it just worked,” Trejo added. “He gives you a lot, in the give-and-take [of a scene]… Sometimes you just get on set, and you automatically just like somebody. He was just like a little brother, but then he also knew his lines and didn’t bump into the furniture.”

In fact, Trejo admitted, he was sometimes the one blowing a take. “We had to do about three takes [of some scenes], because I kept laughing.”Adding to the comedy behind the scenes was Flash star Tom Cavanagh, who directed the episode -- which also features a hilarious Machete reference, in Trejo’s honor.

“I always find that, no matter what you do, you always sort of end up with the perfect director for that episode,” Kreisberg mused. “Having Tom, who’s an actor’s director, and is so funny himself, took this episode to new levels.”

The episode’s lighter tone is par for the course in The Flash’s fourth season, which Kreisberg explained came from the desire to do “something new and something fun,” likening the tonal shift to the series finding its Last Crusade after a few seasons of Raiders of the Lost Ark. “It wasn’t going to get any darker than it got last season, with the possible death of Iris, and the death of HR, and Barry’s future doppelganger [being] the villain… We’re actually sort of commenting on the silliness of the show and wanting everybody to just have a good time, and have it be funny.”

The CW

EXCLUSIVE: 'The Flash' Stars Dish on WestAllen 'Destination Wedding' & Killer Frost's Villain Potential!

Part of that refresh involves the introduction of a new member to Team Flash in Ralph Dibny (Hartley Sawyer), whom viewers also meet in Tuesday’s episode. A passenger on the ill-fated Central City bus, Dibny’s metahuman powers have manifested themselves in newly-elasticised cells, which means his body parts can now stretch to superhuman lengths and sizes. DC Comics fans will also know the character as the Elongated Man.

The CW

“As opposed to a speedster, like Jessie and Wally, where they were both going on similar trajectories to Barry, Ralph’s problems and his hero’s journey has different facets to it, which make it feel fresh,” Kreisberg said of the new meta joining up with Team Flash, despite his less-than-friendly history with Barry Allen (Grant Gustin). “There’s a reason we chose Ralph this season. Some of the things he’s able to do, [viewers will] look back and say, ‘They had a plan.’”

And, he’s even got Breacher’s stamp of approval. “Stretch was cool,” Trejo mused.

EXCLUSIVE: 'The Flash' & 'Supergirl' Musical Crossover: Behind-the-Scenes of Kara & Barry's Tap Dancing Duet

The team will need all the help they can get to take on this season’s big bad, DeVoe -- also know in the DC Comics ‘verse as The Thinker. Not much is yet known about The Flash’s version of this highly-intelligent villain, but according to executive producer Todd Helbing, he’s the “smartest man in the world.”

“[The Thinker] is playing chess. I know that’s sort of cliche to say, but in this case, it’s really true. And as far as he’s concerned, he’s already checkmated Team Flash,” Kreisberg teased of the sinister, super-smart baddie. “He doesn’t really give a s**t what they know and when they figure it out, because, as he’s going to say in an upcoming episode, ‘You’ve already lost.’ It’s really about us trying to figure out how to get ahead of somebody who’s playing so far ahead of you. That’s really the trajectory of the season.”

The Flash airs Tuesday at 8 p.m. ET/PT on The CW.