Olivia Colman pranked Paul Rudd on-air during a BBC radio appearance

• Paul Rudd was on BBC radio when a caller asked him what he would do if a good friend didn't let him know he was in town.
• It turned out it was his friend of over 20 years, Olivia Colman, on the other end of the line.

Paul Rudd got a big surprise while doing press for his new Marvel movie "Ant-Man and the Wasp: Quantumania" in the UK.

While on BBC Radio 1's "Breakfast with Greg James" and taking calls, Rudd spoke to a caller with a thick Welsh accent who was annoyed about something and wanted to get Rudd's take on it.

"So, what would you do if you had a really, like a really good mate, like for over 20 years, and this friend, he doesn't live in England, but he's come to England, and he hasn't told you about it," the caller said. "And then not only has he not told you about it, he's come onto a radio show. What would you do?"

"Oh my God. Oh no," Rudd responded in a panic, feeling the person might be speaking about him.

"By the way, I'm sweating. I'm actually sweating," Rudd said in relief in the full interview.

After coming clean that she'd called in to prank Rudd, she added that she and the "Ant-Man" star really have known each over for 20-plus years. It started when the two were in the same play decades ago.

"Paul used to come and stay on the floor of our rubbish flat in south London and come for Sunday lunch," Colman said. "Paul was properly in the play and I had about two lines, I think."

Things have certainly changed for both actors, who are now major stars. But it's nice to see they are still good friends.