Quote Originally Posted by tdk2fe
Be careful with Misnomer's translation - those two phrases could also be interpreted as having a sexual connotation:

"Me and this girl messed around last night"
"We just f*!@#ed around... the relationship wasn't serious"

tdk
If you're worried about the sexual connotation of "mess around" (which is a rather limited connotation, I think), you can replace it with "goof off."