Or Oasis’s “Champagne Supernova” sounding (to my American ear) like “supin’ over”.

Also, The Lincoln Lawyer has an Australian actor playing a character (Cisco) with a gruff, throaty American accident, but at one point it slips through and he says “Lisa” as “Liser”.

Yeah, that sounds like classic Scouse to me, but you certainly hear it in other UK regional accents.

Is it a regional thing? I have a very "standard" middle-class home counties English accent and I use the intrusive r.

I'm extremely underqualified (non-native speaker) but first time I heard this and paid attention was from Dave Chinner (linux developer) who is australian and he was using a very pronounced linking r.