What is doing an Ozzy Osborne?
Two friends have a conversation on a phone call as below.

A: Look, I just want to say, you've been a good friend.
B: Don't go all mushy on me.
A: Well, I thought I'd say it in case I actually do.
B: Just fect off before I end up doing an Ozzy Osborne on one of these feckin' gerbils.

A feels sorry to B, because B is sharing a room with gerbils due to what A did wrong.
What does 'doing an Ozzy Osborne' mean here?

Question

What is doing an Ozzy Osborne?
Two friends have a conversation on a phone call as below.

A: Look, I just want to say, you've been a good friend.
B: Don't go all mushy on me.
A: Well, I thought I'd say it in case I actually do.
B: Just fect off before I end up doing an Ozzy Osborne on one of these feckin' gerbils.

A feels sorry to B, because B is sharing a room with gerbils due to what A did wrong.
What does 'doing an Ozzy Osborne' mean here?

Answer

Ozzy bit the head off a bat one time  .  So he is referring to killing the gerbil .

Answer

Ozzy Osborne is a famous Heavy metal musician (from those bands that make album covers with screaming demonic figures on the art), so i assume "doing an Ozzy Osborne" would mean doing something very violent or similar to his music on these poor gerbils.
People sometimes use the names of famous people as a verb that is related to what they did as a form of slang, for example some of my friends use "pull/do a Monica Lewinsky" when talking about adultery (as Monica Lewinsky was involved in famous adultery scandal).

Answer

Oh, It's because Ozzy once ripped the head of a bat wih his mounth. (Eww... disgusting)

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