'Trespassing' sensation Adam Lambert recently filmed a special appearance for the Halloween episode of 'Pretty Little Liars' and a clip of it has now surfaced online.

Lucy Hale, who plays the character of Aria Montgomery on the show, tweeted a link to the new preview earlier today (October 9) and it shows Lambert dressed as a vampire while talking to her in the carriage of a train following his musical performance.

Speaking about his involvement in the spooky episode, Lambert explained that it was a lot of fun and he enjoyed the theatricality of the costume he got to wear:

"Yeah that was cool! It was the Halloween episode, so I got to dress up like a vampire which is like my standard Halloween costume that I go to every year. I put my fangs in and had a cool costume, and I got to do a little mini-scene with Lucy Hale who is lovely. I got to perform, so Happy Halloween!"

Meanwhile, it was announced earlier this week that Lambert has been confirmed as one of the headlining acts for San Francisco's Star 101.3 Jingle Ball concert, which is due to take place on December 14, 2012 at The Warfield in San Francisco. Tickets for the event will go on sale this coming Friday (October 12).

The episode is due to be aired in the U.S. on October 23 and you can watch a short part of it below: