The two biggest is the name Shalemar Plaza and in The Citadel DLC, Shepherd wears these Contact Lens that looks like Cat Eyes. Also the Turian Eyes are also cat-like too and also a reference to Geralt's and The Witcher's Eyes!
What do you mean?
ME1 and The Witcher 1 were released in almost the same time (ME was 1 month later), but Witcher 1 was so niche and clunky, it didn’t receive such a massive popularity as ME series did. All this was before The Witcher 3 came out and the series became popular worldwide (by this time ME trilogy was already finished).
you wouldn't understand it. You would have to play the game to understand. But I have a theory, Mass Effect 3 development and the development of the probably original Witcher 3 DlC Probably began around 2012 or so because the DLC was released in 2015 for the original Witcher 3.