Several innuendos all throughout the series, all mild and only adults would understand

Austin is shown shirtless many times throughout the show.

Mostly slapstick comedy, nothing violent, for example:

Season 3, episode 3: When Austin is dancing, his shoe slips off and hits the president in the eye.

Frequent uses of "stupid", "idiot", "dumb", "jerk", etc.

None.

In one episode, an obnoxious kid named Mikey is prone to many tantrums. This can be frightening to some audiences.

Some scenes and episodes may be distressing for very young audiences, for example:

Season 1, episode 18: Austin almost loses his voice.

Season 3, episode 20: Can be seen as frightening for young kids.