How about a monk the learns from an animal? When I did Kung Fu, I practiced the animal forms. Let’s make that work in DnD 5e for the Monk.
Master of Animal Forms
Starting at 3rd level, you gain an animal companion as per the ranger rules. However, you may only choose from the following animals. In addition to the ranger rules for animal companion actions, once per turn, you may spend a ki point as a bonus action to issue a command to your animal companion. You must also pick a time each day when your animal companion will train you. This time lasts for 3 minutes per character level. During this time you may change the animal companion that is training you with no negative repercussions.
|Animal||Page||Bonus Skill||Bonus Save|
|Constrictor Snake||PHB 305||Slight of Hand||Con|
At 6th level, you begin to learn the lessons of your animal companion. You gain proficiency in a skill and saving throw associated with your animal companion. If you are already proficient with the skill or saving throw, then you double your proficiency bonus.
At 11th level, you have continued so deep into your training that you now gain the bonus of your Animal Training class feature for two different animals. You still only have one animal companion.
The Fifth Animal
At 17th level, you have reached the peak of your training, and your animal companion now reflects it. You now gain a dragon wyrmling as your animal companion. It still gains the bonuses as a animal companion as normal (hit points, addition of proficiency to attack, etc), but also has all the skills, immunities, and other creature abilities as a dragon wyrmling. Each day you may choose a different dragon wyrmling type during your training as well as two different animals for your bonuses from your Two Masters class feature.