GREAT BALLS OF FIRE DEPT.

Practical joker MATTHEW MCCONAUGHEY targeted pal JAKE GYLLENHAAL when the two actors hooked up with Tour de France champion LANCE ARMSTRONG for a 15-mile bike ride in Southern California. Armstrong had brought the guys special riding pants, designed for better protection against uncomfortable bike seats -- but just a mile into the ride, Jake began complaining that his butt was on *fire!* Lance and Mat-thew told him to tough it out, just keep pedaling - but the burning became unbearable, so Jake pulled over and quit. The guys cracked up, and Matthew finally confessed he'd rubbed deep-heating arthritis gel -- YeeeOOW! - into the seat of Jake's bike pants. He handed his pal a real cool replacement for his Hot Pants - and after a quick change, the merry pranksters hit the road again.