What's this show(read description)?

It used to come on on Saturdays and it was about these three or four friends who could cross over into an alternate universe and save the day by racing to these castle thingys and it was a cartoon. No one could know about them going there and one of them was like a techie who falls in love with a girl in the universe and they try to find a way to get her out of the universe and into ours. Idk what the name of this show was but I think it was completely CGI but I honestly can't remember.