Depending on your perspective, lenticular covers may be a fun novelty or a vestigial reminder of '90s speculator market excess. It's something DC Comics has employed multiple times in recent years, and the latest arrives in April with "The Button," an upcoming four-part crossover between the "Batman" and "The Flash" ongoing series.

Along with several updates to retailers on pertinent dates for ordering issues of "The Button," DC Comics has released a look at artist Jason Fabok's "Batman" #21, featuring both heroes holding the iconic smiley face button from "Watchmen."

Animated gif of Jason Fabok's 'Batman' #21 cover

Due to the increased production time involved, the lenticular covers for "Batman" #21 and "The Flash" #21 will need to be ordered by retailers more than a month earlier than the nonlenticular versions. For instance, the "Batman" #21 lenticular cover has a final order cut-off of Feb. 13, but orders on the nonlenticular version are due on March 20. Previously, the nonlenticular versions also needed to be ordered further in advance.

Here's a look at the nonlenticular cover of "Batman" #21, combining Fabok's images of Batman and The Flash:

Batman #21 nonlenticular cover
"Batman" #21 nonlenticular cover by Jason Fabok

Also, DC has released a look at Fabok's cover for "Flash" #21 in its nonlenticular form (feel free to use your imagination to add some motion effects). The image seemingly confirms Professor Zoom's involvement in the story -- it's worth noting that the original announcement of "The Button" teased "what begins as a simple investigation soon turns deadly when the secrets of the button prove irresistible to an unwelcome third party – and it’s not who anyone suspects!"

The Flash #21 nonlenticular cover
"The Flash" #21 nonlenticular cover by Jason Fabok.

Both "Batman" #21 and "The Flash" #21 will have "international edition" covers by Mikel Janin which have not yet been revealed. Bleeding Cool observes that these covers are motivated by the fact that the smiley face button image, while public domain in the United States, is a registered trademark in other parts of the world.

"The Button" will take place in “Batman” and “The Flash” #21 and #22, with the “Batman” issues by writer Tom King and artist Jason Fabok, and “The Flash” installments from writer Joshua Williamson and artist Howard Porter. All four issues will have lenticular covers by Fabok.

The story explores the mystery of The Comedian's blood-splattered smiley face button from "Watchmen" showing up in the Batcave at the end of Geoff Johns, Ivan Reis, Phil Jimenez, Ethan Van Sciver and Gary Frank's "DC Universe: Rebirth" #1, released last year; the first time characters from Alan Moore and Dave Gibbons' "Watchmen" have interacted with DC Comics' DC Universe characters. Alan Moore has long made his stance clear that he doesn’t endorse DC revisiting “Watchmen” in any form.

Here’s DC’s official description of the storyline: “Two greatest detectives in the DC Universe unite to unravel the mystery behind a certain blood stained smiley face button stuck in the Batcave wall. However, what begins as a simple investigation soon turns deadly when the secrets of the button prove irresistible to an unwelcome third party — and it’s not who anyone suspects! This is a mystery woven throughout time, and the countdown starts here!”

"Batman" #21 is scheduled for release on April 19; "The Flash" #21 on April 26.