The most famous image of the opening credits is of Van Dyke falling over an ottoman as he enters his living room. However, a second version, showing him sidestepping the piece of furniture instead, was also used. The two openings were filmed back to back and were used randomly throughout the last four seasons of the series. The first season used a completely different opening credits sequence featuring still pictures.
A third variation on the tripping-on-the-ottoman opening was added in later seasons, wherein Van Dyke neither stumbles over nor skips around it, but trips on a corner attempting to do the latter, and recovers without falling.