I believe Lemmy already guested on a version of Waterloo by Dr & The Medics. He was also in the promo for The Ramones' version of that great Who song 'Substitute' which they could do a great version of if they tried. However, if it has to be Abba I want them to do SOS with some gorgeous backing singers. Phil coul also do his party piece in the video and dress up as Agnetha! I doubt it would be difficult to convince him. Does Your Mother Know? would also be a great cover for them to attempt.