The actor, most famous for playing loveable-but-dim binman Robbie Jackson, delighted revellers with his rendition of I'm Gonna Be (500 miles) by The Proclaimers.
The 43-year-old Londoner, who recently became a grandfather, happily posed for selfies and chatted to fans while in town.
Pat Starr, who DJs the weekly karaoke night at Albert's Shed, said he was "a lovely bloke", and "sharp as a button," unlike his EastEnders alter ego.
"He was nothing like his character. He was a really nice guy.
"There was certainly a number of people who recognised him. We do get a few celebs popping in sometimes when they've got a show at the theatre, but he said he was just up visiting friends.
"He was sitting with them and I just said on the microphone 'are you doing a song Dean?' He laughed but then I looked over again and they'd disappeared. I thought 'oh no'. But they'd just moved to another table, and within a few minutes he was up asking what song he should do.
"When they were leaving I said 'he's got to go and feed Wellard,' and then a few more people realised who he was.
"He came and shook my hand at the end of the night and said he'd only come out for a couple but had a great time."
One of the pals the former I'm a Celebrity contestant was visiting was Ryan King, who recently launched his mobile fish and chip shop Fish Heads.
"I had my van at Severn Social," he said. "Dean popped in for a bit then went out in town. I've known him for years when I used to work in Ibiza. He's a great guy."