Apparently "Walking Dead" co-stars Andrew Lincoln and Norman Reedus have been engaged in a bit of a prank war for a while, as Reedus revealed Friday (July 22) at Syfy's San Diego Comic-Con headquarters.

He tells host Will Arnett that it all started when they were doing press in Tokyo and Lincoln asked Reedus how to say "thank you for letting me into your country" in Japanese, because Reedus speaks a little Japanese.

Reedus, being the little scamp that he is, gave Lincoln a phrase to say, which Lincoln then kicked off the press interview with -- but it actually meant "where's the toilet?" And he apparently said it several times to the Japanese press before he realized (based on their reactions) that he probably wasn't saying, "Thank you for letting me into your country."

RELATED: King Ezekiel debuts in 'Walking Dead's' ominious new Season 7 trailer

Reedus also set off a glitter bomb in Lincoln's car. "How much did you fucking put in here?" says Lincoln in the glitter bomb prank video, as bits of glitter and confetti rain down on him and all over his car's interior.

"He was so mad," says Reedus, laughing.

There's no word as to what Lincoln has done in response to any of Reedus' excellent pranks.