This mondegreen first debuted in Jeeves476's AGK series. In the original AGK video (PC Spielen), you can hear the word "sausage eggs" several times when you play the video backwards. This reversed speech is derived from the phrase, Jetzt geht's los, which roughly translates to 'Let's get started' or 'Let's go now'.
At 2:54, Leopold will say "Hey, sausage egg..." quietly while looking at the keyboard. The "Song kits N!" Stated before also sounds similar to "the sausage egg"
At 3:35 when Leopold in the original unreversed video sings his Let's Get Lost song, now he sings the Sausage Egg Song, which he repeats 5 times, with the final 'Sausage Egg' sounding especially well-pronounced. The song then ends with what sounds like "Sausage... HAM??!?!"
The sausage eggs song then became a part of his video intro.
Some users further expand the mondegreen by making him sing this song when his parents cooked sausage eggs for him.