What is 異 doing in the Cantonese translation of the movie title “Us”? I asked a similar question here:
What is 剋 doing in the Cantonese translation of the movie title “Widows”?

The Cantonese title of the film Us has been translated as:

香港譯《我們·異》

Wikipedia also mentions that:

中國大陸、台灣譯《我們》

So, it seems that the Cantonese title is quite different here.

Guangzhouhua-Putonghua only mentions Mandarin definitions.
While Words.HK only gives the following:

語素
1
有分別；同其他嘢唔一樣
different
異口同聲
ji6 hau2 tung4 sing1
saying something together; literally, different mouths but same voice
差異
caa1 ji6
difference
2
唔正常嘅
unusual; extraordinary
異味
ji6 mei6
peculiar smell
異常
ji6 soeng4
abnormal

I'm still not getting the pun, though.
Any ideas?
異 here short for '靈異' (supernatural) or 異形 (alien)

《我們·異》 means "Us - Supernatural" or "Us -Alien" ('alien' here might refer to alien from outer space, but it can also refer to the concept of 'non-native'. In the context of this movies, it implies "unearthly or supernatural being")