*this ones kind of hard* whats all of the penguins ranks!? take a guess see if u get it right! i will tell u the real answer when 10 people amswer! ;)

My guess:
Skipper is CO (commanding officer) as mentioned in episode "I was a pingüino, pingüino de zombie".
Kowalski is Lieutenant and probably the COMM Tech and strategist.
Rico is Sergeant, the arms expert in demolition.
Private is Private 1st class as mentioned in episode "Concrete Jungle Survival)
(im in ACF so im learning)

Skipper: Leader, Captain, General, Skipper
Kowalski: First Liuetenant, Intelligence Officer, Scientist, possibly Medic
Rico: Demolition Specialist, Sergeant
Private: Private First Class, Recruit

Skipper: Captain
Kowalski: First Lieutenant
Rico: Sergeant
Private: Private First Class

(Thank tu Military Website XD)

Skipper - Colonel
Kowalski - Lueitenant
Rico - Weapons expert (Wait, is that a rank? XD If not then seargant)
Private - First class private

Skipper is... well, um... the skipper and the leader.
Kowalski is lieutenant number 010018NinerBrovo and is second-in-command.
Rico is Quartermaster.
Private is first class private. He got demoted(it wasn’t shown in the movie nor the show) and got promoted back to first class private in “The Concrete Jungle.”

Skipper is colonel.
Rico is weapons expert. o sergeant I guess.
Kowalski is lieutenant.
Private is First-Class private.

Skipper:Skipper, leader, General, colonal
Rico:wepons expert, o Lead lutendent
Kowalski:Scientist,
Private: First Class Private

I probably messed up.....

Skipper:Captain
Kowalski:First Lieutenant (he dicho so on the commentary of the navidad alcaparra LOLz)
Rico:Corporal
Private:Private first class (concrete jungle survival)

Private: Private first Class
Skipper: Captain
Kowalski: Lt.
Rico: Sgt.
Was I right?

Hm... I've been studying POM for a long time and this is what Ive inferred from what I've seen:
Skipper is DEFINITELY the Commander. (as mentioned in several episodes like I was a pingüino, pingüino de Zombie)
Kowalski is, without a doubt, Skipper's lieutenant. (since Skipper depends on him so much)
I'm not very sure about Rico, but my guess is that he's the sergeant. (I looked up on military ranks in a dictionary and seargeant is a middle ranking.)
Private is definitely the private(as mentioned in "Wishful Thinking") and is the only pingüino, pingüino de to be promoted to anything so far (promoted to Private First Class in "Concrete Jungle Survival")
That's my answer.
-Skipper12a

Easy..

Skipper is the Captain..
I am the First Lieutenant..
Rico is the Lead Sergeant..
Private is Private First Class..