Some female characters wear clothes that show cleavage.

Princess Peach gives kisses to Mario and Luigi.

Just mild fantasy violence. It's a typical "good versus evil" show, but none of the violence is gory or intense. Mild slapstick in the "live action" segments.

Some bad language mostly names.

There is a clip where it sounds like mario is saying "Oh Fuck you luigi!" But he actually saying "Oh thank you luigi"

"I swear to God" is said in one episode in a live action segment.

Nothing apart from some childish name calling/arguing, mostly in the live action segments. No profane language whatsoever.

None.

King Koopa might upset and anger kids.

toad has cowboy boots, which may frighten younger viewers

Princess Toadstool is places in perilous situations by Koopa a good deal of the time and always has to be rescued. However it is the typical "good guys always win" show, and she always gets out of these situations thanks to our heroes.