Petco is again using the Halloween season to plug private label products and build engagement with a social media contest and in-store events.In-line displays merchandising costumes and themed toys from the retailer's seasonal Bootique private label appeared in stores in early September. A feature in the retailer's Oct. 1 circular promoted the line along with an in-store costume contest that took place on Oct. 14. A home page carousel ad on petco.com, email ads, and Facebook, Twitter and Instagram updates supported.The retailer is also reprising its annual "Make a Scene" photo contest, which runs from Oct. 1-26. Consumers enter by following the retailer on Instagram and sharing a photo of their costumed pet as part of a matching scene with the hashtag #HalloweenSceneContest. A panel of judges will choose three winners to receive $10,000, $3,000 or $1,000. Newtown, CT-based Promotion Mechanics handles. Email ads, an Oct. 16 post on the Petco Community blog, and Facebook, Twitter and Instagram updates promote the contest.Reptiles again got their own Halloween party on Oct. 21, when stores hosted a "Most BOOtiful Reptile" costume contest as part of their monthly Reptile Rally event. Stores also offered 50% off all reptiles and select starter kits that weekend.