With building work ongoing around RTÉ studios, staff and guests alike are on high alert for any unwelcome rodent guests.

As part of 2fm’s "midweek messing" with McVitie's, Carl Mullen has been pranking his co-workers left, right and centre.

Only a week after terrifying Lottie Ryan with a megaphone warning about the Beast from the East, Carl again targeted Lottie - this time pretending there was a mouse under her desk.

This came after Lottie got an awful fright last week, in fact Carl said he actually "felt quite bad about it". He even went as far as to promise to never, ever scare her again.

But his sincerity didn't last long. "So it would be fair to say, one week on, her guard is probably down right now," unrepentant Carl told viewers.

You can see what unfolded above.

Lottie’s horror is almost too real to be funny, even to Carl, but even more amusing is her anger at being secretly filmed - literally - falling head over heels in fright!