One of my favorite anime I've watched as a kid was DOKONJO GAERU (Frog with Guts). It was about a boy who one day fell down and accidentally got a frog pasted on his shirt. The frog somehow survived and as a result the boy now has to live with him.
It was originally a comic drawn by Yasumi Yoshizawa. It got turned into an anime by Tokyo Movie Shinsha in 1972. It ran for 103 episodes.
Here's a clip. Sorry about the poor quality.
There's something to be said about the animation in this show. While crude, it's full of life with great expressions. One of the best uses of limited animation. I wish more shows today (whether it originated in USA or Japan) does that.