Mercedes Lorene pulled off a 50-1 upset to open Wednesday's Pennsylvania Stallion Series event for three-year-old filly pacers at Harrah's Philadelphia, but that proved to be only a sign of an even bigger surprise to come.

Mercedes Lorene trailed the seven-horse field through the first half-mile, but began to pick off rivals one by one during the third panel and defeated the pocket-sitting Corona Again by a neck in a career-best clocking of 1:54.2 after the 1-2 pacesetter Hug A Dragoness broke stride at the top the stretch. Mercedes Lorene earned her third win from 10 starts during her debut season for the father-son, trainer-driver duo of Erv and Marcus Miller. Ronald Michelon, Paymaq Racing and Louis Willinger share ownership of the Western Terror filly, who paid $102 to win in the only division contested over a fast track.

Shortstory Hanover produced an even bigger win payout two divisions later in sloppy conditions as she was sent postward at toteboard-busting odds of 113-1. Andrew McCarthy hustled Lon Frocione's Dragon Again filly off the gate from post eight through a :27-second opening panel before the even-money insider, Some Fancy Filly, looped the early leader. After a second quarter breather to the half in :57, Some Fancy Filly was prompted to three-quarters in 1:25.1 with first over Danika P on the move. However, Shortstory Hanover closed inside down the stretch with second-favourite Terror At Night and prevailed over that filly foe by half a length in 1:54.3. The Brett Bittle trainee returned a whopping $229.20 to her backers while notching her first win of the season from nine starts. Some Fancy Filly finished one and a half lengths behind in third.

Sayulita and Tony Morgan managed to pull off a mild 14-1 upset in the rainy fifth and final division of the day. Gapped back in fourth-place early on, the Somebeachsomewhere filly moved underway at the half and eventually prevailed by one length in 1:55.2 over 1-9 favourite Keystone Riptide, who closed up the inside off a pocket trip. Richard Lewis trains the winner for owners David Banks and Layfield Horses LLC. She paid $31 to win.

The Chris Oakes-trained Nips Beach Girl ($10.60) won the fastest of the five $20,000 divisions in 1:52.4 and was one of five winners on the card driven by David Miller. Susan Oakes and Chuck Pompey's homebred Somebeachsomewhere filly advanced from second-to-last through fractions of :27.1, :55.3 and 1:23.2, and reeled in the front-striding Addy Girl for the victory by three-quarters of a length.

The streaking Dismissal ($7.20) and driver Brett Miller were also victorious in a Stallion Series division for owner/trainer Michael Hall. The daughter of Western Terror was on the move early from fourth and followed Quiet Cove's cover before overtaking her and holding sway the rest of the way to win by two lengths in a career-best clocking of 1:53.4. She extended her win streak to six in a row.