No, it’s not Halloween at the Hynes Convention Center this weekend. The elaborately costumed crowd masquerading around Boylston Street is here for Anime Boston, a three-day festival of fun and, let’s be honest, weirdness that celebrates Japanese animation, comics, and pop culture. More than 25,000 people, many of them dressed as their favorite anime characters, are attending this year’s gathering, making it the largest such event in New England (and the fifth largest anime convention in the US.) Anime Boston includes plenty of panels, gaming events, screenings, art shows, and vendors, and also special guests, notably Akira Takarada, a Japanese actor famous for his roles in Godzilla movies. Other celebrity guests include Cherami Leigh, an actress who has voiced characters in several anime series, including “Peach Girl” and “The Sacred Blacksmith”; voice actress Cassandra Lee Morris; and Japanese singer LiSA, who performed Friday night for an overflow audience familiar with the theme music she’s done for various anime series.