In addition Czech has the sound ř, which is almost impossible to pronounce unless you learn it in childhood. I don't know of any other language with that sound. Tongue-twisters will almost by definition explore the weird sound combinations in any language, but Czech is a fruitful hunting ground for these!

Interestingly, the geographically close but linguistically unrelated Hungarian makes up for all the vowels that Czech eschews. They're almost polar opposites in vowel usage.

Phoible lists four phoneme inventories with the Czech <ř> ([r̝] in IPA), three of which are varieties of Czech and the fourth being Lyélé in Burkina Faso: https://phoible.org/parameters/1214D761CC44F5F017FD63EA26B45...

However, Phoible is not exactly complete. E.g. Wikipedia has a different list: https://en.wikipedia.org/wiki/Voiced_dental,_alveolar_and_po...

It sounds very familiar to me, I am Slovenian and our sound Ž sounds similar to ř

I know that Czech also has Ž, but to my ears we pronounce it harder, so words like žrelo, or žrebiček ... it kind of comes close.

It sounds even more like Morse code when you realize that the double Ts are a longer sound than the single Ts. It really is like dots and dashes.