Two minutes later the Bulldogs were in the lead when Tim Lafai sliced through to set up Josh Morris before Kasiano and Williams secured their doubles to complete the ambush.
It looked like being a comfortable night at the office when the Bulldogs scored two tries in the opening 12 minutes, before the Dragons turned to Dugan - who on Friday agreed to terms for another four years in the 'red v'.
With little else working for the home side, Dugan scored two brilliant individual tries, the first with two big right foot steps before a chip and chase on the stroke of halftime to give his side an unlikely lead.
He played the crucial role in Nightingale's try just after the restart and when Sam Perrett's missed intercept attempt gifted Daniel Vidot a four-pointer, the home side appeared in control.
"We probably let ourselves down a little bit ... I think they had six penalties in a row which made it really difficult," Canterbury coach Des Hasler said of his side's mid-game slump.
"It was difficult for us to build momentum and then when we were down their end a couple of times we squandered a couple of opportunities.
"Once we got a bit of footy in the second half we were able to get on a bit of a roll."
Dragons coach Steve Price was furious with his side, defeat ending whatever slim chance they had of making the top eight.
"20-8 up, we started to play like a footy team that was behind and that was the most frustrating thing," Price said.
"We started to throw balls out of our arse as opposed to playing field position, kicking long.
"We didn't play with any smarts at all."
- AAP
