IRVINE, Calif. (KABC) -- It's a full-on battle of the burgers. In-N-Out is taking fast-food rival Smashburger to court over a stacked-patty creation.The Irvine-based company claims Smashburger's "triple double" comes way too close to In-N-Out's "double double" burger.In-N-Out filed a trademark infringement lawsuit Monday, saying Smashburger's latest menu addition could confuse customers.The double double has been a staple at In-N-Out since 1963.Denver-based Smashburger was founded in 2007 and launched the "triple double" last month.