Spare a thought for the vets at London Zoo who have been looking after Lucifer, the 30 stone lion.
The Asian big cat's been given a heath check to make sure he's fit and ready to join a new breeding group for the endangered species in a new location.
Zookeepers had to train the 11-year-old lion, named after his studbook number 666, to lie on his side so they could administer an anesthetic with an injection.
He's part of a special Zoological Society of London campaign, Lion400, aimed at raising £5.7 million to save the species.
Vets gave him an all-over examination in his enclosure down to checking the inside of his mouth to check his teeth.
He's been given a clean bill of health and will move later this week.
So how do you count more than 19,000 animals, large and small, for London Zoo's annual stock take?
Martin Stew went to find out.
London Zoo are counting all their animals today from the huge gorillas to the tiny ants.
Mark Habben, manager of the Regents Park zoo, explains why they do an annual stocktake.
More than 700 seals have been recorded in the Thames Estuary.
In the first ever count by air, land and sea, the Zoological Society of London found hundreds of grey and harbour seals along the Thames and in small creeks and rivers.
"After a carefully-managed introduction process, the two girls are getting along famously with the rest of the group," say zookeepers, "With dominant male Lucky taking a particular liking to Mo - who quite enjoys the flirty attention."
Martin Stew has been enjoying the weather at London Zoo ahead of the first part of ITV's behind the scenes series on the famous attraction, which airs at 8pm tonight.
Tammy the anteater will be out roaming ZSL London Zoo from tonight, when a number of late night openings begin.
She's at her most active during the evening and early in the morning, but her eyesight isn't up to much, so the clumsy 12-year-old is getting a minder to make sure she doesn't get into trouble. We speak to keeper Caroline Westlake.