I was once home sick from work and watching daytime TV between naps on the sofa. After I'd been watching an episode of Columbo for about three hours I realised it was actually an episode of Columbo, Diagnosis Murder, and Murder She Wrote (I think) consecutively with a few common bit-part actors and I'd nodded off between them :)

Edit: I remember it as being Dick van Dyck in all of them, but it was a long time ago and that seems unlikely!