The 2001 reference in this image is here probably due to Missile39's reasoning as to why he had Rei sing Daisy Bell in this video. Since HAL sang the song as a reference to the IBM7094 (the first computer to use a synthesized voice to sing), he found it fitting that Rei should also sing it.
Netsu IjouPan Kogekoge ni NacchattaAdachi Rei (Avogado6)Adachi Rei Seisan Koujou (Avogado6)Rei (Otonashi AF)Mawaru Sentaku NetHyper Sign(?)