Nashville, Tenn. — The instant a running back stops, turns and tosses the ball back to a quarterback, someone yells: "Flea flicker!"

It's that moment of trickery when a coach tries to catch an opponent by surprise, whether it's the quarterback suddenly turned wide receiver or a running back turned passer. Or even a left tackle scoring a touchdown.

For every unplanned play that earns a name like the Immaculate Reception, there's a gimmick cooked up by coaches to catch a defense by surprise. Not all gadget plays go down in NFL history like Home Run Throw Back, best known as the Music City Miracle. And all any coach ever wants is a trick play picking up a big chunk of yards.

Better yet? Points on the scoreboard, of course.

"It's fun to know that you've designed it this way, they've reacted the way you would have anticipated, and it's just rewarding," said Titans coach Mike Mularkey, who has notebooks filled with trick plays dating back to his days as offensive coordinator with the Pittsburgh Steelers. "That's any play. We put a lot of time in on every one of these plays. No different for gadgets and specials. There's a lot of them, and we're expecting them to hit."

With the NFL at the halfway point, plenty of teams have dipped into the playbooks for something special. Johnny Hekker threw a 28-yard pass for a first down on a fake punt by the Rams in Week 2. Aaron Rodgers converted a flea flicker into a 41-yard pass to Davante Adams in Week 3. Jaguars running back Corey Grant took a direct snap 58 yards on a fake punt in a big win over Baltimore in London.

The best play trick play this season may have come in Chicago on a 2-point conversion against Minnesota, with Mitchell Trubisky scoring on an intricate play based on timing, execution and misdirection. Trubisky handed off to Jordan Howard, who gave the ball to tight end Zach Miller who pitched to the wide-open Trubisky.

"Les Steckel ran that play in Tampa," Mularkey said. "They stole that play from Les. Many other teams have run that play."

Bears offensive coordinator Dowell Loggains saw Steckel run that play in 2000 with the Buccaneers and added it to his personal notebook. Loggains met Steckel while working for the Titans and said Steckel called the play "Doughnut."

"So I've always had this play ...," Loggains said. "But you've got to have Zach Miller. You got to have a tight end or a Mike Alstott that you trust with the ball handling. So it's just an option play off that. That's where the play came from. Coach Les Steckel deserves all the credit for it. We just installed it 17 years later."

When the play call came into the huddle, Trubisky said there was a smile all around as the Bears knew they would score and tie the game against the Vikings.

"We practice it, go over it over and over again, and it came to life in the game," Trubisky said. "So that was really cool to see. Those are the kind of plays you do get excited for."

So was what Tyreek Hill did for Kansas City on Sunday.

His "Hill Mary" came on the final play of the first half at Dallas. Hill caught an easy toss from Alex Smith at the Cowboys 42 and started toward the goal line with three blockers in front. The speedy Hill motored around Orlando Scandrick at the 25, cut behind two blocks from Demarcus Robinson inside the 10 and sidestepped overpursuing linebacker Anthony Hitchens to finish the stunning TD untouched.

Every football player loves the chance to throw the ball, too. One of Seattle punter Jon Ryan's favorite plays remains from the 2014 NFC championship when he threw a touchdown pass on a fake field goal.

"You don't really have time (to worry)," Ryan said. "Everything happens so quickly you don't' really have time to get nervous or excited or anything. You're just concentrating on executing."

Not every play works. Pittsburgh tried a reverse option pass in the 2015 opener only to have receiver Antonio Brown sacked for an 8-yard loss. Miami coach Adam Gase said quarterbacks get a bit irritated when a team lets other players throw too many passes.

"I've been around one where you better complete it, it better be good," Gase said. "But, when you've got guys that can do a lot of things and cause a lot of problems and defenses have to prepare for it, it's a real weapon."

Gadget plays aren't designed merely to give fans a reason to stand up and cheer. Or pick up first downs or score touchdowns. Coaches also want to force opposing coaches to waste precious time in a short game week preparing for a play that may not be called again.

"That's why you try to give variety," Gase said. "You try to make it hard for defensive coordinators to prepare for you."

In the NFL, lots of players were quarterbacks or running backs in high school. Mularkey puts a star next to a player's name during draft evaluations if someone also has skills that make him an option for a trick play. He even pulled out some of his notebooks and showed the Titans some of gadget plays he ran as coordinator in Pittsburgh starting in 2001. In 2002, Mularkey said the Steelers ran nine 2-point plays and scored on eight.

Mularkey, whose Pro Bowl running back DeMarco Murray threw a touchdown pass last season , still has a batch of exotic 2-point plays ready and waiting.

"And we practice them every week," Mularkey said.

AP Sports Writers Steven Wine, Tim Booth, Will Graves and Andrew Seligman contributed to this report.