>>95270537the only flapjack crew member on OK KO (discounting minor production and sound design people shared between all shows) is story editor Dave Tennant, who had been a story editor on season 3 of flapjack (he was also story editor on SMFA and head of story on season 1 of Uncle Grandpa), plus a few early eps had Jessica Yost (color stylist on Flapjack and Regular Show) do color styling
There's definitely indirect ties to flapjack, with crew members from AT, Regular Show, SMFA, and the netflix dreamworks Home series