U2 are currently finishing up the South American leg of their '360' world tour, with Muse supporting them for the stint.
Following their final date on the continent at Sao Paulo's Morumbi Stadium, the groups popped into the local Bar Secreto, says The Sun.
Bono and Larry Mullen appeared on stage for a quick performance and were joined by Muse drummer Dom Howard. They then proceeded to perform a cover of Talking Head's 'Psycho Killer'.
Muse frontman Matt Bellamy was not present for the collaboration, but reports suggest that U2 guitarist The Edge took on vocal duties to perform renditions of The Rolling Stones' 'Miss You' and David Bowie's 'Let's Dance'.
Both bands are taking headline slots at major festivals this year, with U2 booked to perform Glastonbury and Muse confirmed for Reading and Leeds festivals.
U2 recently claimed the record for the 'Biggest Tour Ever' after grossing more than £340 million ($558 million) for their current tour.
Watch U2 and Muse perform Talking Head's 'Psycho Killer' below: