The cartoon always had one chase scene where the characters did just that---jumping on *anything* stacked vaguely cube-like (rocks to cross a river, etc.---even IIRC a bunch of moon rocks in an episode where they went to the moon). 
But yes, pre-Super Mario Bros. video games didn't have much in the way of plots, thus for the cartoons they had to create a lot of stuff wholesale... in Pac-Man's case, playing up the world he lived in (Pac-Land, full of various pac-pun-names), along with the ghost monsters working for a Darth Vader-ish figure out how to find the source of the Pac-people's power-pellets so he could conquer their world...
-B.

But yes, pre-Super Mario Bros. video games didn't have much in the way of plots, thus for the cartoons they had to create a lot of stuff wholesale... in Pac-Man's case, playing up the world he lived in (Pac-Land, full of various pac-pun-names), along with the ghost monsters working for a Darth Vader-ish figure out how to find the source of the Pac-people's power-pellets so he could conquer their world...
-B.