Burger King may not have been able to lure its biggest rival into a charity-minded collaboration, but four other chains have stepped in to fill the McWhopper void.

Denny's may be the largest and best-known of the lot, but the fast-casual chain will be joined by Krystal (a Southern chain similar to White Castle), Wayback Burgers and Giraffas (a Brazilian chain with 10 Florida locations) in offering Peace Day co-branded burgers on Sept. 21.

Here's the note Burger King posted to its Tumblr:

Since each of these partnership-minded chains had already proposed the idea to Burger King, it's safe to say they're on board:

we're in! let's hash it out over some hash browns. https://t.co/tYjlrILUNw

— Denny's (@DennysDiner) September 1, 2015

Here are the original tweets from each chain that volunteered:

We have a #SteamyProposal for @BurgerKing. A new way to #SettleTheBeef for #PeaceDay. Accept, your royal Burger-ness? pic.twitter.com/ZhppAGsKqC

— Krystal (@Krystal) August 26, 2015

.@BurgerKing, we won't leave you hanging. #McWhopper #WhipleWhiple #SettleTheBeef pic.twitter.com/wCFiYuGOPO

— Wayback Burgers (@waybackburgers) August 26, 2015

Hey @BurgerKing, let's settle this Brazilian style. #PeaceDay #McWhopperProposal pic.twitter.com/gKpAsIIjhV

— Giraffas USA (@GiraffasUSA) August 27, 2015

hey @burgerking how about a Slampper© or a Whammper© or a Whoppaslamus-rex© or something? pic.twitter.com/zWHXfgIPYV

— Denny's (@DennysDiner) August 27, 2015