He’s a walking advertisement for breakups gone wrong.

An aging adman’s former boy toy is allegedly refusing to leave the spacious Park Avenue pad they shared — and has launched a harassment campaign in a bid to wring a financial settlement out of their split, according to a lawsuit.

The choice weapons in Glenn Allen Rice’s reported war of attrition against his ex-boyfriend Steven Novick include dirty laundry, clutter and even Novick’s aging dog, Novick charges in Manhattan Supreme Court papers seeking a court order to oust Rice.

Rice has also climbed into the tidy Novick’s bed while the 79-year-old Novick is away, leaving it a mess, claims the retired Grey Global executive who sits on the boards of builder Toll Brothers and the Julliard School.

The pair was romantically involved for less than a year before their July split, during which Rice pledged to leave Novick’s 2,200-square-foot home, which includes three and a half baths and a guest quarters, by summer’s end.

But he would not leave, and his alleged antics included locking Novick’s pooch, Mitzi, into rooms with expensive rugs without food or water until the dog was forced to urinate and defecate on the carpets.

Rice claims he decided against moving to Texas and lost out on financial opportunities, such as the chance to buy his own home, once Novick promised to support him financially.

A judge ordered Rice to stay out of Novick’s bedroom, living room and office and stop any “anti-social behavior” until the two sides go back to court in November.