I can reference three other instances foreshadowing him boinking his mother.
1- admits to have had dreams of fucking his mother, often proclaims his dreams to be prophetic.
2- has defended the act of incest between mother and son, claiming that it would be beneficial for them. Even states that it would be better if the mother was in menopause so they don't have to worry about impregnation.
3- In public, Chris has lovingly sighed and cooed at his mother, saying things like "you're so pretty".

I'd love to see a 4 hour long Chis-Chan Mad Lads special some day.