"It's nice to finally get scripts offered to me that aren't the ones Tom Hanks wipes his butt with"

Jim Carrey is making a joke about the quality of scripts he has been provided in the past. He is suggesting that the scripts he has actually been provided in the past were of such low quality that even Tom Hanks, a popular and highly regarded star, would not even consider them. He is revealing his relief that he is now being provided scripts of a greater quality, which he implies are good enough for Tom Hanks to utilize them for something besides cleaning his butt.