Joe Rosenthal
Joe Rosenthal (1979 - ?) was Danny's best friend, whose boundless libido was (barely) balanced by Danny's levelheadedness. Joe and Danny were friends in high school, and became roommates in college. Joe took a dislike to Joyce (which later, strangely, evolved into an attraction) and, in his sophomore year, Howard. He also had an almost-but-not-quite longer-term relationship with Sarah Clinton. He was also abducted by the Head Alien, becoming part of his mind-controlled army during "Year Zero," but was eventually saved by Sal and company.
Joe returned to college, and eventually graduated with a degree in engineering (inspired by his hidden love for geeky things such as Transformers). Not long after entering graduate school, he was dragged to SEMME by Sal and forcibly drafted into the group. Danny and company were told he was dead, while he joined the ladies of Squadron 48- virtually heaven for him. However, Joyce, who'd developed an attraction to Joe, was devastated by his antics with Squad 48; she even masqueraded as Anti-Joyce and tried to seduce him. Joe, in a show of maturity, rejected her for her own good.
After Sal went rogue, Joe was moved to Squadron 128, where he soon found an annoyance in Jason. When Sal returned to face justice, Joe began working for Professor Doc, developing new inventions for SEMME. He also began an online relationship with someone he thought was Robin DeSanto, but actually turned out to be supermarket clerk Rachel. Joe also helped build the U.S.S. Destiny. During the Martians' invasion, Joe's inventions- such as Joyce and Walky's battlesuits, and Ultra Car- proved crucial to the outcome of the battle. Joe, Rachel, Danny and Howard piloted Ultra Car onto the Martian mothership, and helped destroy it. On his return, Joe built a makeshift Martian resurrection chamber to revive Walky and, hopefully, other fallen members of SEMME. Presumably, Joe and Rachel are happy together.
Recently, Joe (with Danny and Ultra Car) attempted to rescue Jason from Monkey Master, and was injured as a result. Presumably he pulled through.