Colbert celebrates 'paper anniversary' of Mueller's Russia probe Mueller's investigation into Russian meddling turns a year old on Thursday.

Robert Mueller's investigation into Russian meddling turns a year old on Thursday, and Stephen Colbert said he knows exactly how the special counsel might celebrate.

"I am so excited," Colbert said Wednesday. "Mueller was appointed one year from tomorrow.

"Of course, the first is anniversary is traditionally the paper anniversary, and with any luck, that is is what Mueller is going to be serving Donald Trump with."

Mueller on Wednesday subpoenaed Jason Sullivan, an adviser to Trump’s longtime confidant Roger Stone, as a part of the ongoing investigation into Russian meddling in the 2016 presidential campaign.

The "Late Show" host also joked about news that a grand jury had been impaneled in Washington.

"By law, it has to be a jury of Donald Trump's peers, so guess it's Sean Hannity, the cast of 'Shark Tank' and a cheeseburger," Colbert said. "You are what you eat."