Walliams is on the show this year as a panellist and joins Simon Cowell, Alesha Dixon and Amanda Holden on the panel.
"It's rare to see him on a show with someone camper than him!" Lucas told Heat.
"It's good that Simon Cowell's got someone there who will challenge him and tease him. I don't think Simon quite realises what he's let himself in for."
He added: "It's also perfect for David to do. David's achieved so much, not just in comedy, but also acting on stage, in drama.
"I think he should be made a Sir for all the charity stuff he's done. Or at least a Dame."
Walliams was the most searched-for Britain's Got Talent judge on Yahoo! after the first show, but slipped below Holden and Dixon in the rankings after the second week.
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Watch David Walliams talking about Simon Cowell below: