Johnny Depp is known for never blending into the background ... but at a recent Vegas event, he literally started eating it.

While attending Drink Las Vegas -- a four-day event across multiple hotels -- at Park MGM last night, the "Pirates of the Caribbean" actor stopped to pose for photos ... and, well ... munch on some plants.

In the video obtained by TMZ ... Johnny bit a leaf from the photo call's backdrop before chewing on it in front of the event's attendees.

After spitting out the green ... the Oscar-nominated actor went back for round 2 and chomped on an even bigger piece of the step-and-repeat wall.

Johnny seemed to be in good spirits ... so it looks like he was just having a bit of fun with a few photographers!

Well, Johnny has a lot to be happy about ... the lawsuit against his band, Hollywood Vampires, was dismissed by a judge.