I came across this image on Facebook from the website Learn Something Every Day:
Is it true?
No, but they sleep a lot
Koalas have an extremely slow metabolism because they are herbivores that eat eucalyptus exclusively. Eucalyptus is a poor nutrient (high fibre, low protein).
Because of this, they tend to sleep or rest a lot.
Koalas spent about 4.7 h eating, 4 min travelling, 4.8 h resting while awake and 14.5 h sleeping in a 24-h period.
While it's a lot, it isn't even close to the 22 hours in the question. Also, note that they spend almost 5h eating. This is again because of their diet and slow metabolism.
Nagy & Martin (1985) found that free-ranging koalas spend c. 80% of the time resting or sleeping. Such large periods of inactivity are believed to enable koalas to maintain relatively low energy requirements, and thus to use a poor quality diet (Cork & Sanson, 1990).