He chases his tail vigorously, often spending several minutes just glaring at it, sighing and occasionally hissing in its direction.

The only way we can take him to the vet for his annual checkup is to give him a hefty dose of Acepromazine (aka, kitty tranq). This causes him to stumble around drunkenly purring, with his inner eyelids partway across his eyes. It's both heartbreaking and hilarious but, most importantly, it helps him to not scream bloody murder and soil himself in terror at the vet's office.

A bizarre side effect we've noticed in the several years we've been giving him this drug is that it seems to have a permanent effect on his mood. Each year after taking him to the vet, he's been noticeably less anxious when we've had friends or family over. His hissing and growling has diminished, not slowly over time but instead in stages, each time after a visit to the vet. Makes me wonder what he'd be like if we gave him this drug more often (an experiment that will not be carried out, thank you).

If we play with the laser pointer, he likes it at first but after a while he starts acting paranoid. Twitching and jerkily looking all around as though the SPIDERS! THEY'RE ALL OVER HIM! GET THEM OFF, GET THEM OFF! It takes him at least an hour to get over the jumpiness. We don't play with the laser pointer anymore.

He chews everything and excessively licks furniture and doors.

I'm quite sure Indy is beyond weird and is a mentally ill cat. But he's our mentally ill cat.