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All four of them have appeared on "The Simpsons" as guest stars

 last month 

✅ Correct! They've all made guest appearances on The Simpsons.

 last month 

Good morning ;-))

And another try: they all have musical ambitions... The ‘Beatle’ speaks for itself, Lisa Kudrow played in a band in ‘Friends’ and sang herself, David Duchowny has recorded several albums, just like Leonard Nimoy...

 last month 

👎 Wow! I didn't realise David Duchovny or Leonard Nimoy are musical. I'm not convinced by either upon 1st listen but maybe I'll give them a chance!

 last month 

I clearly prefer David... ;-))

 last month 

My initial thoughts were that David was more to my liking too!

all are the stars of the 90s? Friends, X-files etc?

 last month 

👎 I'm not sure if Paul McCartney fits that description... so that's not the link I'm looking for.

okay, second chance, but again Paul McCartney does not fit very well. I\ll try to fit it in though.
Three of those artists are with the Slavic/Jewish-Ukrainian roots. Except Paul, but Paul supports Ukraine very much, plays a lot of concerts there, so he also is strongly connected with the region :)

 last month 

👎 I'm always amazed by some of the connections that appear in the answers. Is this really true?

alexanderkass has answered correctly now - they all made guest appearances on The Simpsons.

They’re all southpaws 💁‍♂️

 last month 

👎 Is that true? It's amazing some of the links you all find if it is 😆

alexanderkass has now answered correctly... they all made guest appearances on The Simpsons.