The Britain's Got More Talent star recently taped a new pilot for the classic ITV quiz show, which was originally fronted by Roy Walker from 1986 to 1999.
Speaking to Digital Spy, Mulhern argued that it would be "a real shame" if the project was to fail, recalling an incident from filming where a contestant guessed the phrase "ham fisted" as "slapping the meat" as an example of the fun that viewers would miss out on.
"I'd forgotten how funny the show was," he admitted. "I'd be gutted if it didn't [get picked up] and I don't see why it wouldn't.
"Its biggest selling point is its playability at home and because it's been off screens for so long. I know there's been reruns of it, but young kids wouldn't have been aware of it so it's a new game for them."
Mulhern added that although he aims to put his own spin on Catchphrase, it has been a struggle to avoid repeating Walker's famous lines.
"I did read something that [Roy] said he would still liked to have done it," he said. "I've got the most respect for him because he did the game so well.
"The hardest thing was not saying his catchphrases. You can't say 'say what you see' because that's synonymous to him - what I came up with was 'the clue's on the screen but what does it mean?'
"If it does go to series then I need someone to put an electrode on me so every time I do do it I get a shock."
Mulhern is also preparing for a role in Woking's Dick Whittington pantomime, which will run at the New Victoria Theatre from December 7, 2012 to January 6, 2013.
Watch a classic Catchphrase clip below: