There are multiple Hellboys, but there's only one Ron Perlman.

I am the Hellboy ...

Ron Perlman, star of Hellboy (2004)
and Hellboy II: The Golden Army (2008)

They are the Hellboy ... 

David Harbour, star of the 2019 Hellboy reboot

Deadpool 2's Jack Kesy, recently cast as Hellboy
in a second reboot

I am the walrus ... 

Perlman in the BBC series The Capture (2019-present)

Goo goo g'joob.