UrsusArctos: The correct lyrics are "three bugs" since they refer to Red, Blue and Yellow ladybugs! The song being sung is Tentoumushi no sanba (てんとう虫のサンバ, "The Ladybug's Samba"), in this case covered by Megumi Ogata (Shinji), Yuko Miyamura (Asuka), Miki Nagasawa (Maya), and Junko Iwao (Hikari) and included as a bonus track on the Neon Genesis Evangelion Addition Album. Originally released by CHERISH (the husband-wife duo of Yoshitaka and Etsuko Matsuzaki) in July 1973, it was a huge success within Japan and remained popular and easily recognizable throughout the 1990s, although I don't know if this song continues to be played at weddings into the 2020s.
