IT'S a bird, it's a plane — it's superbulge! "Superman Returns" star Brandon Routh is supposedly giving the suits at Warner Brothers fits because of his prodigious package of masculinity. The 26-year-old beefcake's extra-large endowment is said to be so distracting through his skin-tight costume that producers may have to shrink him during post-production. "It's a major issue for the studio," a "Superman Returns" production source fretted to the London Sun. "Brandon is extremely well-endowed and they don't want it up on the big screen. We may be forced to erase his package with digital effects."