The voiced 'th' sound /ð/, as in the word “mother” /ˈmʌðɚ/ is often replaced with these sounds by non-native speakers (and may even be used in some native dialects):
TH initial sentences
I sat in the third row at the movie theater.
The thunder scared my dog, Theo.
I was thankful my coffee was in a thermos.
He threw to third base in a hurry.