Warning: The following contains spoilers for The Flash #761 by Joshua Williamson, Howard Porter, and Steve Wands, on sale now.
As Reverse-Flash enters into his endgame to defeat The Flash once and for all, the supervillain assembled his own Legion of Zoom. Thawne went through the timeline and recruited Barry Allen's most brutal foes onto one big team. Not to be outdone, Max Mercury, who has made it his life's work to study the Speed Force, opened a portal and enlisted some Speedsters that haven't been seen in a while. Dark Flash, the Flash from Kingdom Come, and the Earth-2 Jason Garrick are a few of the Speedsters who have come to help the Flash defeat Thawne and his Legion. One of the more interesting recruits is Krakkl, a friend from Wally West's past.
Krakkl's first appearance is in The Flash #136 in the story, "The Human Race." The character is created by Mark Millar, Grant Morrison, and Paul Ryan and started off as Wally West's imaginary friend. When.a young boy, West talked to what he believed was an imaginary friend through the radio. Over time he stopped listening to the radio and just figured Krakkl was a figment of his imagination. West is reminded of Krakkl when a group of intergalactic gambler-aliens arrive at Earth and present West with an ultimatum. West can either be part of a race throughout the space-time continuum, or the world will be destroyed.
West, of course, agrees to the race and finds his competitor is Krakkl, his "imaginary" friend from all those years ago. Krakkl actually comes from the planet Kwyzz and is a race of radio-frequency beings that are lightning-fast and can communicate using radio frequencies. Though excited to see each again, West and Krakkl's reunion is tainted by having to compete against each other for the safety of their respective worlds. Ultimately, Krakkl sacrifices himself to save Flash, Earth, and his own home planet and race.
Krakkl's appearance is what a radio frequency might look like if it came to life. It is also unavoidable to compare Krakkl's appearance with another popular character, Sonic the Hedgehog. Besides his incredible speed, Krakkl has shades of blue on his body and even has Sonic-like spikey tails for hair. Sonic the Hedgehog is one of gaming's most recognizable and popular characters. Add to this Sonic's super-speed, and there's no wonder why a version of him pops up in a Flash comic.
Krakkl doesn't do anything in The Flash #761 that particularly stands out. Krakkl, along with the other Speedsters, help send the members of the Legion of Zoom back to their own timelines. But just because Krakkl isn't a part of the Flash Family by blood, Barry points out that by him heeding Max Mercury's call to assemble makes him and the other non-blood Speedsters, like Steadfast and Fuerza, part of the family. The Flash Family is as much a Brother/Sisterhood of Speedsters as it is a family united by blood relatives.
There's no doubt that Krakkl is a Sonic-inspired character. With Sonic's easily identified appearance and popularity, it's easy to see why writers originally created Krakkl to be part of the DCU, and with The Flash #761, this cements Krakkl's well-deserved place as a member of the Flash Family.