Silly question, I know! As I'm looking on solar at 2nd year program selections, I've found some things I'm incredibly interested in but unfortunately don't have the prereqs for!
For example I would be interested in doing a double major (honours) in Gerontology and Cognitive Science of Language, but i did not take health and aging, or the psych courses required for cog sci lang.

What should I do now? any suggestions?

What program are you currently in? Some allow you to continue on in second year with a general major, for example 'social science level 2.' You can also choose to register in a major you do have the prerequisites for and then switch in third year to the program you would rather be in. Or you could try to take the prerequisites you need during summer school if they're offered.

Right now I'm in Humanities! Do you know if this would allow me to continue with a general major? Thanks a ton though

You can check the course calendar to see if the general program is offered. If it's not listed, then it sometimes still does exist but it's not a "degree program" because it's meant more for people whose GPA was too low for any degree program but not low enough to get kicked out - sort of an interim thing while they get their grades up.

Whether you do end up doing general humanities or pick an alternate major for second year before switching into the major you want, just make sure that you take as many required courses as you can from the major that you want, so you won't be too far behind. That's especially important if you want to take a double major - there's not generally a lot of room to get behind on course requirements there.

You should be able to continue on in general humanities in second year. In most cases getting into a degree program in second year is easier than getting into one in third year. You may want to choose a program for second year, even if you don't think you want to stick with it, just as a back up. Who knows, you may like it and end up minoring in it or something.
And then like starfish said just make sure to take as many of the required courses as you can from the program you want to apply to in third year.