The act of making an intoxicated late night run to McDonalds.
When it's late night after boozing hard and/or smoking weed and you are hungry. Someone needs to go on a McMission to McDonalds.
"Hey man.... I got the munchies, who's going on a McMission?"
The result of a professional athlete getting a big head and growing his hair out cause he thinks he's so cooler than he is. When u make it to the big leagues they call it "The Show." Players refer to hair as lettuce. Hence Show Lettuce.
"Damn, look at Bryce Harper sportin that show lettuce! Better put some mayonnaise on that show lettuce rookie!"