There's Herp All Up In My Derp!

-For example, when he transforms into BigChill, Steve's parental urges are overwhelming, making him fret over the kids more than usual. When he's Wildmutt his desire to please takes over, prompting him to act like puppy that just wants chin scratches and praise after mauling a Demogorgan.

-Spideymonkey makes Steve more excitable and energetic, while Rath makes Steve brutally blunt and angry.

-Despite having to use XLR8 a lot, Steve has a hard time adapting to the alien's rapid pace of thought. In a fight he's fine, but when it comes down to remembering complicated dates and times he gets confused and anxious easily. (( The reason WHY Steve has to use XLR8 so much is because he accidentally hit the Omnitrix inside his car, transformed into Humungousaur, which then resulted in him completely wrecking his baby. )))

-The Omnitrix will sometimes respond to Steve's emotions and give him an alien that he desperately needs for a situation, or one that reflects what he is feeling the most. So when he's mad, the Omnitrix may transform him into Rath even though he wanted to become Spidermonkey.

-Ironically, Steve's desire to have kids is what made BigChill reproduce. He accidental triggered the aliens hormone's into high gear.