Secret skill

There are several secret skills in The Sims 2.

Yoga
Sims who have three or more Body points get the "Do Yoga" self-interaction. Yoga is not only a skill in its own right, but doing yoga builds fitness and Body skill. However, skill at doing yoga is related to Body skill, not yoga experience. Unlike many Body-building activities, yoga does not cause a fast drop in the Hygiene meter.

Painting
The more paintings a Sim paints, the more he will be paid for them--even if (especially if) he has already maxed his Creativity.

Meditation
Meditation is a skill that Sims from teens on up acquire if they have three Logic points and seven or less Playful. While a Sim meditates, their motives; such as Energy or Hunger do not decay; neither does their Aspiration. This makes meditation useful to "save" a Platinum mood for later, such as for a promotion. If you have your Sims meditate for a certain amount of time, they could learn to teleport. Meditation takes half a Sim hour to begin and another half an hour to stop.

Dancing
This is a hidden skill that involves Sims getting better at the activity of dancing. Sims who are at the bottom end of the skill have very entertaining actions and moves. Teen Sims that get to the top of the dancing skill can qualify for the Tsang Footwork Scholarship (University required). A Sim with a relatively good Dancing skill has access to the social "Entertain--Bust a Move", which is available to use on Sims at a relatively low Lifetime Relationship of 20-30 and increases lifetime relationship by one or two points.

Pool
A skill learned by playing pool/billiards. Teens can receive the Phelps-Wilsonoff Billiards Prize of §1000 for having a high pool skill (University required). The better a Sim is at the Pool skill, the more likely he is to succeed at Hustling pool.