It's all greek to me

[Guapo]

Portuguese sometimes sounds Slavic too.

I noticed that too, maybe because it is stronger sounding than other Romance languages. Greek to me sounds like a mixture of Spanish and Finnish, very soft

To me it sounds like my cousins.

Nicko, Nick and Nickolas?

[Treffie]

For example, in Portuguese "s" is pronounced "sh" so "Lisboetas" (natives of Lisbon) is pronounced "Lishbo-ay-taash."

And instead of the soft Spanish suffix -cion with accent over the "i", the same suffix is "cao" in Portuguese with a strange "~" accent over the a. Portuguese also has a harsh /dz/ sound.

Compare Spanish "yo soy" (I am) containing soft "c" sound and Portuguese "eu seu" containing harsh "sh" sound. "eu" and "seu" kind of smash together cacaphonously.

More specifically, Lisboa is pronounced Lizh-bo-ah in Portuguese, the -zh sound is very common and I think that's one of the reasons people assume that it's a Slavic language at first.