That was a joke as noticed by many that it hold no meaning. From hollywoodreporter

Josh Brolin's casting as Cable in Fox's Deadpool 2 has been greeted with both joy and confusion online. After all, doesn't Brolin already play Thanos in the Marvel Cinematic Universe? Is that even allowed? (The answer to both: Yes!)

Deadpool star Ryan Reynolds played up those fan anxieties with a tone-perfect tweet.

"The f—, Fox! You can't play 2 characters in the same universe!! Josh Brolin was in Sicario and I was in Sabrina The Teenage Witch," he tweeted Wednesday.

(For the record, Brolin was not in Sabrina the Teenage Witch and Deadpool is not in the same universe as Avengers.)

Ryan just played on fan confusion.

That was a joke, as noticed by so many. From hollywoodreporter

Josh Brolin's casting as Cable in Fox's Deadpool 2 has been greeted with both joy and confusion online. After all, doesn't Brolin already play Thanos in the Marvel Cinematic Universe? Is that even allowed? (The answer to both: Yes!)

Deadpool star Ryan Reynolds played up those fan anxieties with a tone-perfect tweet.

"The f—, Fox! You can't play 2 characters in the same universe!! Josh Brolin was in Sicario and I was in Sabrina The Teenage Witch," he tweeted Wednesday.

(For the record, Brolin was not in Sabrina the Teenage Witch and Deadpool is not in the same universe as Avengers.)

Ryan just played with the fan confusion.