Does Polish have the 'Big Comfy Couch' kids' show?
Doesn't ring a bell. But quite probably it did to the author of this sentence.
Can wygodna mean comfy? One of the accepted translations is 'cozy'?
Yes it can. http://dictionary.cambridge.org/dictionary/english-polish/comfy
I guess nobody reported this translation.
Funny that wygodny means favorable in Russian. Can never be too sure with these Slavic cognates.
Can couch be used instead of sofa as that is the term we always used for this particular piece of furniture.
Yes, of course, it works.