  The Higgs and some of the Standard Model superpartners may have been
copiously produced at LEP and the Tevatron without being detected. We study a
novel scenario of this type in which the Higgs decays predominantly into a
light hidden sector either directly or through light SUSY states. Subsequent
cascades increase the multiplicity of hidden sector particles which, after
decaying back into the Standard Model, appear in the detector as clusters of
collimated leptons known as lepton jets. We identify the relevant collider
observables that characterize this scenario, and study a wide range of LEP and
Tevatron searches to recover the viable regions in the space of observables. We
find that the Higgs decaying to lepton jets can be hidden when the event
topology mimics that of hadronic backgrounds. Thus, as many as 10^4 leptonic
Higgs and SUSY decays may be hiding in the LEP and Tevatron data. We present
benchmark models with a 100 GeV Higgs that are consistent with all available
collider constraints. We end with a short discussion of strategies for
dedicated searches at LEP, the Tevatron and the LHC, that allow for a discovery
of the Higgs or SUSY particles decaying to lepton jets.
