The phrase "cl plz," originally comes from the outbreak of Call of Duty challenge lobbies that were a result of the PlayStation 3 becoming jailbroke in early 2011. People would sign up on gaming sites just to request, ask, and spam for challenge lobbies. Majority of the times, the new members would simply post, "cl plz."
In today's modern time, the phrase is used to describe new members that sign up just to leech and request things.
alfonso1337: *Signs up on a gaming forum* Spams "cl plz" everywhere.
n00b69: *Signs up on a gaming forum* Can someone resign my game save? Can someone host me a lobby? Can someone hack me prestige 20?
xXHomovolXx: That kid is a cl plz