He and William Katt had great chemistry.  I think by the time they were a few eps in, they were making up their own dialog half the time.  And remember how Bill would eat dog biscuits and neither Ralph nor Pam would mention it, they'd just look at him funny?  That killed me.

Yep!  I can't help but smile when Bill's eating those dog treats!  Yeah, it will be sad the next time I watch the show.

The first time he was a security expert and he killed his girlfriend by accident, and he kept trying to bribe Columbo with a high paying job.  Columbo catches him with a contact lens in Culp's trunk.

Second time he was the GM of a football team and he creates an alibi of being in the owners box during a football game when he is actually murdering Dean Stockwell in a swimming pool with a piece of ice. 

The third time he is a maker of motivational films and uses subliminal cuts to get a client to go to the lobby at a specific time so he can shoot him. 

The shoes being tied wrong was Robert Conrad.  Yes, I have seen these episodes WAY too much.

I remember Robert Culp killing a guy at his gym and Columbo could tell that the victim hadn't tied his own shoes, so that's how he got him.  I think the other time he killed either his wife or girlfriend.  But I don't remember any details.

Is 3 times a record on Colombo?  If it is, I never would've guessed it was held by Mr. Culp.  I'd have put my money on Patrick McGoohan.