Postl started his career in the Fox Valley Wrestling Alliance (FVWA), under the ring name Hardcore Wonder. In 2005, Postl appeared with National Wrestling Alliance territory NWA Wisconsin as "The World's Sexiest Midget" Shortstack, where he won the NWA Wisconsin X Division Championship. He also won the SSW Tag Team Championship with Devin Diamond, from The Pretty Hott Thangs (Ryan Kross and Josh Maxim) on May 19, 2006, in Oak Creek, Wisconsin. He relinquished the title after signing a contract with World Wrestling Entertainment.

On February 23, 2007, the character's name was changed to Hornswoggle on WWE's website and all references to the name "Little Bastard" were removed. The meaning of Hornswoggle is to swindle, cheat, hoodwink, or hoax. On the March 2 episode of SmackDown!, Hornswoggle attacked John "Bradshaw" Layfield and Michael Cole. Afterward, Finlay intimidated Cole, warning him to refer to Little Bastard as "Hornswoggle." On March 30, Hornswoggle helped Finlay beat Mr. Kennedy by performing a senton bomb off a stepladder onto Mr. Kennedy, essentially copying Kennedy's move, the Kenton Bomb. SmackDown! announcers Michael Cole and JBL immediately referred to the move as the "Lepreton Bomb". During the Money in the Bank ladder match at WrestleMania 23, Mr. Kennedy hit Hornswoggle with a Green Bay Plunge off of a ladder when Hornswoggle tried to interfere on the behalf on Finlay. On the following edition of SmackDown!, Finlay attacked Mr. Kennedy after his match and challenged him to a handicap match with Postl as Finlay's partner. Before the match, Mr. Kennedy apologized for hurting Hornswoggle. Finlay accepted his apology and formed a team with Kennedy.

He made his in-ring return on the April 18 episode of SmackDown, defeating Matt Striker after a Tadpole Splash. As part of the 2008 WWE Supplemental Draft, Hornswoggle was drafted to the ECW brand along with Finlay. At Night of Champions, Hornswoggle and Finlay challenged John Morrison and The Miz for the WWE Tag Team Championship, but failed to win.

On April 13, 2009, Hornswoggle was drafted to the Raw brand, without Finlay, as part of the 2009 Supplemental Draft. Hornswoggle then entered into a feud with Chavo Guerrero, in which they competed in a series of comedy gimmick matches each week determined by the weekly Guest Host for Raw (Texas Bullrope Match, Blindfold Match, Falls Count Anywhere, etc.). The program began on July 7, 2009 on WWE Superstars and continued on to Raw. Hornswoggle won every match in this feud.

Postl's next storyline began the October 26 episode of Raw, when after several weeks of wearing D-Generation X clothing, Hornswoggle received legal notification that he was no longer allowed to wear it. Later on in the night, he got his revenge by helping the Raw guest hosts, Kyle Busch and Joey Logano, put DX against each other and John Cena for the WWE Championship at Survivor Series. On the December 21 episode of Raw, Hornswoggle tried pressing charges against DX for assault on him, but later dropped them when DX agreed to make him DX's official mascot. On the January 18, 2010 episode of Raw backstage, Hornswoggle and Triple H confronted Big Show, The Miz and Jon Heder. Triple H made the match a six-man tag team match: DX and Hornswoggle against The Big Show, The Miz and Jon Heder which ended after Hornswoggle pinned Heder.

On the November 29, 2011, holiday edition of SmackDown, Hornswoggle won a battle royal, by lastly eliminating Sheamus, to receive a wish from Santa Claus (Mick Foley). With help from Sheamus, Hornswoggle wished for the ability to verbally communicate. With this ability, Hornswoggle became the special guest ring announcer for the David Otunga and Sheamus match on the following week's SmackDown. On the January 6, 2012, episode of SmackDown he defeated Heath Slater in an Over the Top Rope Challenge. Later that month, Hornswoggle formed an alliance with Justin Gabriel, feuding with the former Intercontinental Champion Cody Rhodes and Heath Slater, he also accompanied Gabriel to the ring at the Elimination Chamber pay-per-view in a losing effort against United States Champion Jack Swagger. On the March 23 episode of SmackDown, Hornswoggle was added to Theodore Long's WrestleMania XXVIII team as its personal mascot.

He made a return on October 12, 2012, when he was found with a Randy Orton doll. Ricardo Rodriguez wrecked it and continued looking for the real Orton. After a period of inactivity, he returned to Raw in November, associating himself with The Great Khali and Natalya. He was injured (storyline) by Big E Langston on the January 11, 2013 episode of SmackDown, after Khali and Natalya lost to Dolph Ziggler and AJ Lee. He returned on the March 17 episode of Raw, to celebrate St. Patrick's Day, only to be interrupted by Bad News Barrett.

On the April 15, 2014 episode of Main Event, Hornswoggle turned heel after revealing himself as the mascot for 3MB (Heath Slater, Drew McIntyre and Jinder Mahal). In the following months, he faced El Torito numerous times, losing a WeeLC match at Extreme Rules (Postl says this was the best match of his career) and a hair match at Payback, resulting in his head being shaved. On June 12, 2014, McIntyre and Mahal were released by WWE, and ending 3MB. In July on Superstars, Hornswoggle accompanied Slater for his match with Adam Rose, and was kidnapped by the Rosebuds, who transformed him into a mini-Rose. On the August 19 episode of Main Event, Hornswoggle joined his former rivals, Los Matadores (including El Torito), as their second valet. Hornswoggle donned a cow suit and was referred to as La Vaquita (meaning "the little cow"), to compliment El Torito, who was dressed as a tiny bull. Los Matadores went on to be defeated by Heath Slater and Titus O'Neil. That same week, on Superstars, his name was tweaked to La Vaca (meaning "the cow"), when he teamed with El Torito to defeat Slater and O'Neil. On the September 29 episode of Raw, Hornswoggle turned heel once again and became Heath Slater and Titus O'Neil's (Slater-Gator) mascot, the Mini-Gator. After the breakup of Slater-Gator, Postl took time off from WWE television to undergo arthroscopic shoulder decompression surgery in March 2015.

Postl starred in the film Leprechaun: Origins, a reboot of the Leprechaun film series. Hornswoggle regularly appeared in the WWE web series The JBL and Cole Show, until its cancellation in June 2015. He made his video game debut as Finlay's manager in WWE SmackDown vs. Raw 2009.

On the December 15, 2016 episode of Impact Wrestling, titled Total Nonstop Deletion, Swoggle made an appearance as the partner of Rockstar Spud in the Tag Team Apocalypto match. After turning on Spud in the Tag Team Apocalypto, Swoggle would square off with Lashley, and knocked himself out when he attempted a spear on Lashley. He would then appear on the January 5, 2017 episode of Impact Wrestling, where he would defeat Rockstar Spud, causing Spud to quit. On January 19, episode of Impact Wrestling, he would then team up with Robbie E in a losing effort against Aron Rex and Spud. On the April 27 episode of Impact Wrestling, Postl was paying Rockstar Spud some attention and ruffled Spud's hair in what was intended to be an amusing gimmick with the fans - however Spud took exception to this and as he was chasing Postl, the situation concluded with Postl running up the entrance ramp, after losing his trousers (pants). Later that same show, Postl would viciously attack Spud using a hammer, causing unknown leg injuries. On June 1, Spud returned to Impact, entering through the crowd and attacking Swoggle with a hammer, like Swoggle had done to him. On November 13, 2017, his profile was removed from Impact Wrestling's website. Reportedly, Swoggle was never signed to a contract by Impact Wrestling. confirming his departure from the company.