Ok, so we should be thinking of a lovable, cuddly, stuffed penguin sitting down after having gorged itself on herring. NOW comes the hard part. With this image firmly etched on your eyeballs, you then scetch a stylizied version of it. THAT requires talent. But the simple, single penguin would be the logo, and the others would just be that cuddly penguin being used as an actor in some tableau.
Penguins are fun.
No good reason, really. So you can have a real live penguin on a CD cover, for example, and people will get the association. You can't really do anything with a logo like that. A contest was proposed to pick a suitable Penguin logo - but from what I can see of the email at the time, Larry Ewing's famous Penguin painting won more or less by popular acclaim. Tux naturally leapt to mind.