Sonntag bei Omi is an unreleased song by Rammstein.
Background
This song has existed since the recording sessions for Reise, Reise and Rosenrot.
In March 2004, it was found in the GEMA database, which is how its existence is confirmed and its length is known. As of today, the song has been removed from GEMA.
Paul was asked about Sonntag bei Omi in an interview, he said that it is "something really disgusting that Till came up with" and is "too heavy even for a Rammstein release".
Because of that and the song's title, which translates to "Sunday with Granny", it is speculated that the lyrics are based on Till's poem "Großmutter" released in his book Messer.