Kommer du med bussen = Do you come by bus/with the bus. Jeg kommer med kaken = I'll bring the cake.
I remember the sentence 'Katten kommer med.' or something similar. This is not a good Norwegian sentence. 'Katten kommer med oss.' is much better. I would say: 'Kommer du med meg?' not 'Kommer du med.'
Instead of 'Kommer du med meg?' you can say: 'Blir du med meg?' I prefer to use 'blir'.
Hmm, that's weird actually. I assume from your name that you're native and know what you're telling about. That's why i find what you say worrying as in the course it's always kommer med and never kommer med meg/oss/dem. Is it really that bad? What kind of bad? Unusual, uneducated, obsolete or sth?
I would never say: 'Kommer du med?' I say: 'Blir du med/blir du med meg?' So you can just forget about the 'Kommer du med' sentence. Say 'Blir du med' or Blir du med meg'/'Blir du med oss' if you say the sentence in Oslo.
To RobertAGun1. My grandfather who was Danish, would probably say: 'Kommer du med.' Maybe this was something people said in Østfold in the 1940s.
Witnessing language evolve is interesting. I was a student in Østfold in the 1940s. I don't recall my parents saying anything other than, "Kommer du med." I should however add that when I began university in Oslo I learned the dialect my family spoke was considered by academics to be "farmers' Norwegian".