What's the worst part of your vehicle to keep clean??

Submitted to The Shop

For me it has to be TWO things (now)

1- The Undercarriage!
Always the hardest for me to keep clean and make sure rust is not building up on any structural areas and always a problem when it's too late.

AND

2- The Interior!
This was never, ever a problem to keep the interior clean until little ones came along. Either the pets or the kids makes the interior a nightmare to keep clean now-a-days!!!

Whats yours??