The Klimpalooners are the secondary antagonists of the Phineas and Ferb episode "The Klimpaloon Ultimatum". They are a team of male synchronized swimmers working for their boss Mittington Random.
The Klimpalooners first appeared in the episode wearing giant parkas when Phineas, Ferb and their friends head over to Random's Himalayan fortress to rescue the legendary creature Klimpaloon. Anticipating the kids' arrival, the Klimpalooners managed to capture the kids and transport them into the lair, where they are horrified to see several deformed Klimpaloon clones and that Random has a device that would seemingly extract Kimpaloon's life force. Random then revealed to the kids of his true plan to infuse Klimpaloon's life force into his latest swimwear line for a fortune, and the Klimpalooners take off their parkas to reveal their new old-timey bathing suits before engaging into a musical number with Random to prove his point.
However, Ferb causes a power outage, which allowed the kids to free Klimpaloon from its restraints and run off with it from Random's fortress back to the 4th Annual Tri-State Area Music Show Awards. An angry Random orders the Klimpalooners to go after the kids, but they start to shiver due to the extreme cold weather since they previously discarded their parkas during their musical number, prompting an annoyed Random to head back to the awards show himself.
It is unknown what happened to the Klimpalooners after their boss was exposed of his plot, though it may be implied that they lose their jobs since Random lost his career and was briefly turned into a warthog (due to an elixir that Heinz Doofenshmirtz made for the award show).