My favorite part of “It’s Always Sunny in Philadelphia” is about to take his talents to a land of giant monsters.

Charlie Day in talks to join the cast for Legendary Pictures’ Pacific Rim that Guillermo del Toro is on board to direct, writes Variety.

The pic, which already stars “Sons of Anarchy” star Charlie Hunnan, is about an alien invasion that threatens earth and the humans who come together to defend it.

Day will play a professor. Legendary had no comment on the casting.

Travis Beacham penned the script. Production is expected to get under way this fall.

The project has gained momentum in recent months since del Toro came on board to direct after his previous pic At the Mountains of Madness was put into turnaround at Universal.

Legendary had shown strong interest in Ildris Elba to take a role, and at one point Alexander Skarsgard was being pursued. Skarsgard passed because of his “True Blood” commitments.

